Weighted average duration of cash flows
Weighted Average Duration Of Cash Flows For Remediation Expenditure
Weighted Average Duration Of Cash Flows For Remediation Expenditure
Proportion of ownership interest disposed
Proportion Of Ownership Interest Disposed
Proportion Of Ownership Interest Disposed
Remeasurements
Remeasurements, Netting [Member]
Remeasurements [Member]
Triple ‘A’ G7 sovereign entities (AAA)
AAA G7 Sovereign Entities [Member]
AAA G7 Sovereign Entities [Member]
Disclosure of contingent liabilities [line items]
Disclosure of contingent liabilities [line items]
Independent actuarial funding valuation, period
Defined Benefit Plan, Independent Actuarial Funding Valuation, Period
Defined Benefit Plan, Independent Actuarial Funding Valuation, Period
Disclosure of other provisions [line items]
Disclosure of geographical areas [line items]
Net amount presented in statement of financial position
Net Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Agreements Or Similar Agreements In Statements Of Financial Position
Net Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Agreements Or Similar Agreements In Statements Of Financial Position
Purchases of property, plant and equipment
Purchase of property, plant and equipment, classified as investing activities
Property and other taxes
Tax expense other than income tax expense
Wages and salaries
Wages and salaries
Capital expenditure prepayments
Capital Expenditure Prepayments [Member]
Capital Expenditure Prepayments
Inventory valuation reserve
Inventory Valuation Reserve
Inventory Valuation Reserve
Entity File Number
Entity File Number
Cash dividend
Dividends paid, ordinary shares
Deferred tax
Deferred tax expense (income)
Schedule of intangible assets
Disclosure of detailed information about intangible assets [text block]
Liability for claims and claims adjustment
Liability For Claims And Claims Adjustment [Member]
Liability for Claims and Claims Adjustment [Member]
Levels of fair value hierarchy [domain]
Levels of fair value hierarchy [domain]
Equity shareholders of the parent from continuing operations
Comprehensive income from continuing operations, attributable to owners of parent
Proportion of defined benefit plan, buy-in-transaction insured
Proportion Of Defined Benefit Plan, Buy-In-Transaction
Proportion Of Defined Benefit Plan, Buy-In-Transaction
Subsidiary Of Associate [Domain]
Subsidiary Of Associate [Domain]
Subsidiary Of Associate [Domain]
Derivative cash flows included in capital expenditure
Adjustments To Cash Flows Classified As Investing Activities For Derivative Cash Inflow Related To Capital Expenditure
Adjustments To Cash Flows Classified As Investing Activities For Derivative Cash Inflow Related To Capital Expenditure
Treasury shares, market value
Treasury Shares, Market Value
Treasury Shares, Market Value
Sales between segments
Elimination of intersegment amounts [member]
Before exceptional items and remeasurements, netting
Before Exceptional Items And Remeasurements, Netting [Member]
Before Exceptional Items And Remeasurements [Member]
Net defined benefit liability (asset) [axis]
Net defined benefit liability (asset) [axis]
FVOCI debt and other investments
Non-current financial assets measured at fair value through other comprehensive income
The Narragansett Electric Company
The Narragansett Electric Company [Member]
The Narragansett Electric Company
In 2 to 3 years
Later than two years and not later than three years [member]
Fuel stocks
Current fuel
Cash and cash equivalents [abstract]
Cash and cash equivalents [abstract]
Emission allowances
Current Emission Allowance
Current Emission Allowance
Gross amounts offset
Gross financial assets set off against financial liabilities subject to offsetting, enforceable master netting arrangements or similar agreements
6 – 12 months past due
Later than six months and not later than one year [member]
-100 basis points change in discount rate
Sensitivity Analysis, 50 Basis Point Change Decrease In Discount Rate
Sensitivity Analysis, 50 Basis Point Change Decrease In Discount Rate
Cash generated from operations – continuing operations
Cash flows from (used in) operations
Other
Other tax effects for reconciliation between accounting profit and tax expense (income)
Disclosure of interests in subsidiaries, joint ventures and associates
Disclosure Of Interests In Subsidiaries, Associates And Joint ventures [Table Text Block]
Disclosure Of Interests In Subsidiaries, Associates And Joint ventures
Gain on disposal of equity instruments measured at FVOCI
Other comprehensive income, net of tax, gains (losses) from investments in equity instruments
Finance income and costs
Finance income (cost)
Disclosure of detailed information about right-of-use assets
Disclosure of quantitative information about right-of-use assets [text block]
Disclosure of detailed information about borrowings [table]
Disclosure of detailed information about borrowings [table]
Electricity swaps
Commodity Derivatives - Electricity Swaps [Member]
Commodity Derivatives - Electricity Swaps [Member]
FVTPL investments
Non-current financial assets at fair value through profit or loss
Disclosure of associates
Disclosure of interests in associates [text block]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Electricity transmission plant and wires
Electricity Transmission Plant And Wires [Member]
Electricity Transmission Plant [Member]
Disclosure of detailed information about borrowings [abstract]
Disclosure of detailed information about borrowings [abstract]
Exceptional items and remeasurements, netting
Exceptional Items And Remeasurements, Netting [Member]
Exceptional Items And Remeasurements [Member]
5.809% Notes Due 2033
5.809% Notes Due 2033 [Member]
5.809% Notes Due 2033
Intangible assets and goodwill
Intangible assets and goodwill
Income statement
Statement of comprehensive income [abstract]
Statement of changes in equity [line items]
Statement of changes in equity [line items]
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Attributable to:
Comprehensive income attributable to [abstract]
Basic earnings per share (continuing) (in GBP pence per share)
Basic EPS (continuing) (in GBP per share)
Basic earnings (loss) per share from continuing operations
Total other revenue
Other Miscellaneous Revenue, Non IFRS15
Other Miscellaneous Revenue, Non IFRS15
Longevity swap
Derivatives, amount contributed to fair value of plan assets
New England Hydro-Transmission Electric Company Inc.
New England Hydro-Transmission Electric Company Inc. [Member]
New England Hydro-Transmission Electric Company Inc. [Member]
UK electricity balancing costs
Balancing Costs
Balancing Costs
Derivative liabilities - current
Current Derivative Financial Liabilities [Member]
Current Derivative Financial Liabilities [Member]
Exchange adjustments
Increase (decrease) through net exchange differences, goodwill
Disclosure of geographical areas [table]
Disclosure of geographical areas [table]
New York
NEW YORK
Dividends declared before financial statements authorised for issue
Dividends proposed or declared before financial statements authorised for issue but not recognised as distribution to owners
10% increase in commodity prices
Commodity Price Risk, Ten Percent Increase [Member]
Commodity Price Risk, Ten Percent Increase [Member]
Included within share of post-tax results of joint ventures and associates
Included With Results From Joint Ventures And Associates [Abstract]
Included With Results From Joint Ventures And Associates
Generation
Generation [Member]
Generation [Member]
Derivative financial liabilities
Current derivative financial liabilities
0 – 30 days past due
Current [member]
Prepayments
Current prepayments
Statement of financial position
Statement of financial position [abstract]
Other costs
Other operating income (expense)
Other interest
Interest expense on other financial liabilities
Cover [Abstract]
National Places LLP
National Places LLP [Member]
National Places LLP
Maximum
Maximum [Member]
Bulk annuity policies
Structured debt, amount contributed to fair value of plan assets
Related party transactions
Description of accounting policy for transactions with related parties [text block]
Financial instruments
Financial Instruments Subject Enforceable Master Netting Arrangement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities)
Financial Instruments Subject Enforceable Master Netting Arrangement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities)
Fair value change
Fair Value Change [Member]
Fair Value Change [Member]
Net interest income on pensions and other post-retirement benefit obligations
Interest income, defined benefit plans
Number of US Superfund sites
Number Of US Superfund Sites
Number Of US Superfund Sites
Increase (decrease) in defined benefit plan expense due to reasonably possible increase in actuarial assumption
Increase (Decrease) In Defined Benefit Plan Expense Due To Reasonably Possible Increase In Actuarial Assumption
Increase (Decrease) In Defined Benefit Plan Expense Due To Reasonably Possible Increase In Actuarial Assumption
Unused amounts reversed
Unused provision reversed, other provisions
Disclosure of amounts recognised in the statement of financial position
Disclosure Of Defined Benefit Plan Recognised In Statement Of Financial Performance Explanatory [Table Text Block]
Disclosure Of Defined Benefit Plan Recognised In Statement Of Financial Performance Explanatory [Table Text Block]
Provisions
Description of accounting policy for provisions [text block]
Subsidiaries
Description of accounting policy for subsidiaries [text block]
Non-net debt financing cash flows
Cash Inflows, Non-Net Debt Financing Cash-Flows, Classified As Financing Activities
Cash Inflows, Non-Net Debt Financing Cash-Flows, Classified As Financing Activities
Short term investments, restricted
Short-Term Investments, Restricted
Short-Term Investments, Restricted
Classes of intangible assets other than goodwill [axis]
Classes of intangible assets other than goodwill [axis]
Disclosure of sensitivity analysis for actuarial assumptions [table]
Disclosure of sensitivity analysis for actuarial assumptions [table]
Number of different categories of financial and other investments
Number Of Different Categories Of Financial And Other Investments
Number Of Different Categories Of Financial And Other Investments
Profit after tax from discontinued operations
Profit (Loss), After Tax, Before Gain (Loss) On Disposal, Discontinued Operations
Profit (Loss), After Tax, Before Gain (Loss) On Disposal, Discontinued Operations
Entity Shell Company
Entity Shell Company
Disclosure of joint operations [table]
Disclosure of joint operations [table]
Share premium account
Share premium
Cash flows from financing activities
Cash flows from (used in) financing activities [abstract]
Bonds
Current bonds issued and current portion of non-current bonds issued
Retained cash flow/adjusted net debt
Retained Cash Flow Ratio
Retained Cash Flow Ratio
Contract liabilities [abstract]
Contract liabilities [abstract]
Classes of liabilities [domain]
Classes of liabilities [domain]
Remeasurement and foreign exchange effects recognised in the statement of other comprehensive income
Decrease (increase) in net defined benefit liability (asset) resulting from gain (loss) on remeasurement in other comprehensive income
Cash surrender value of life insurance policies
Restricted Balances, Cash Surrender Value Of Life Insurance Policies [Member]
Cash Surrender Value Of Life Insurance Policies [Member]
Total comprehensive income for the year
Comprehensive income
Diluted earnings per share (continuing) (in GBP pence per share)
Diluted EPS (continuing) (in GBP per share)
Diluted earnings (loss) per share from continuing operations
Schedule of reconciliation of the net defined benefit asset (liability)
Disclosure of net defined benefit liability (asset) [text block]
Basis of preparation
Disclosure of basis of preparation of financial statements [text block]
Net amount presented in statement of financial position
Net financial liabilities subject to offsetting, enforceable master netting arrangements or similar agreements in statement of financial position
Grain LNG
Grain LNG [Member]
Grain LNG
Interest In Other Entities [Domain]
Interest In Other Entities [Domain]
Interest In Other Entities [Domain]
Dividends received
Dividends Received, Related Party Transactions
Dividends Received, Related Party Transactions
Other
Other Segments [Member]
Other Segments
Document Fiscal Period Focus
Document Fiscal Period Focus
Cash at bank
Balances with banks
Interests In Other Entities [Abstract]
Interests In Other Entities [Abstract]
Interests In Other Entities [Abstract]
Total assets
Assets
New England Hydro-Transmission Corporation
New England Hydro-Transmission Corporation [Member]
New England Hydro-Transmission Corporation [Member]
Litigation Case [Domain]
Litigation Case [Domain]
Lease income
Operating lease income
Gains (losses) on exchange differences on translation of foreign operations
Gains (losses) on exchange differences on translation of foreign operations, before tax
Tax
Description of accounting policy for income tax [text block]
Non-current assets
Non-Current Assets [Member]
Non-current Assets [Member]
Provision for post closing capital expenditure
Provision For Post Closing Capital Expenditure
Provision For Post Closing Capital Expenditure
Associates [domain]
Associates [domain]
Related amounts available to be offset but not offset in statement of financial position
Amounts Subject To Enforceable Master Netting Arrangement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities) [Abstract]
Amounts Subject To Enforceable Master Netting Arrangement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities) [Abstract]
Total current tax from continuing operations
Current tax expense (income) and adjustments for current tax of prior periods
Goodwill
Description of accounting policy for goodwill [text block]
Credit risk
Credit Risk
Credit risk [member]
Trading Symbol
Trading Symbol
Amounts receivable
Amounts receivable, related party transactions
Types of interest rates [axis]
Types of interest rates [axis]
Revenue
Total revenue from continuing operations
Revenue
Derivative cash flows included in revenue
Increase (Decrease) Through Derivative Cash Flows Included In Revenue, Other Financing Derivatives
Increase (Decrease) Through Derivative Cash Flows Included In Revenue, Other Financing Derivatives
SONIA
Sterling Overnight Index Average - SONIA [Member]
Sterling Overnight Index Average - SONIA
Issued in rights issue (in shares)
Increase (decrease) In number of Rights Issued (in shares)
Increase (Decrease) In Number Of Rights Issue
Increase (Decrease) In Number Of Rights Issue
Entity Address, City or Town
Entity Address, City or Town
Net amount
Net financial liabilities subject to offsetting, enforceable master netting arrangements or similar agreements
Insurance company and non-qualified plan investments
Restricted Balances, Insurance Company And Non-Qualified Plan Investments [Member]
Restricted Balances, Insurance Company And Non-Qualified Plan Investments
More than 3 years
Later than three years [member]
Purchases of goods and services, related party transactions
Purchases Of Goods And Services, Related Party Transactions
Purchases Of Goods And Services, Related Party Transactions
Borrowings
Borrowing facilities
Disclosure of borrowings [text block]
Share capital
Issued capital [member]
Gain (loss) on assets held at end of year
Gains (Losses) Recognized In Profit Or Loss, Fair Value Measurement, Assets (Liabilities) Held At End Of Period
Gains (Losses) Recognized In Profit Or Loss, Fair Value Measurement, Assets (Liabilities) Held At End Of Period
Other non-current liabilities
Other non-current liabilities
Other non-current liabilities
Classes of other provisions [domain]
Classes of other provisions [domain]
Other equity reserves
Other reserves [member]
Discount of issue price, percentage
Discount Of Issue Price
Discount Of Issue Price
Cash outflows relating to restructuring activities, operating activities
Cash Outflows Relating To Restructuring Activities, Operating Activities
Cash Outflows Relating To Restructuring Activities, Operating Activities
Gas plant – mains, services and regulating equipment
Gas Plant - Mains, Services And Regulating Equipment [Member]
Gas Plant - Mains, Services And Regulating Equipment [Member]
Disclosure of quantitative information about right-of-use assets [table]
Disclosure of quantitative information about right-of-use assets [table]
Entity Emerging Growth Company
Entity Emerging Growth Company
Pensions and other post-retirement benefit assets
Non-current net defined benefit asset
Treasury shares, gifted (in shares)
Treasury Shares, Gifted
Treasury Shares, Gifted
Non-current liabilities
Non-current liabilities
Non-Current Liabilities [Member]
Non-current Liabilities [Member]
Trade and other payables
Description of accounting policy for trade and other payables [text block]
Financial instruments
Financial instruments subject to enforceable master netting arrangement or similar agreement not set off against financial assets
Other movements
Increase (Decrease) Through Other Changes, Investments Accounted For As Equity Method Investments
Increase (Decrease) Through Other Changes, Investments Accounted For As Equity Method Investments
Disclosure of reconciliation of changes in goodwill [line items]
Disclosure of reconciliation of changes in goodwill [line items]
Restructuring Activities [Domain]
Restructuring Activities [Domain]
Restructuring Activities [Domain]
Severance costs (excluding pension costs)
Termination benefits expense
Issue price (in GBP per share)
Issue Price, Per Share
Issue Price, Per Share
Provision for UK electricity balancing costs
Provision For UK Electricity Balancing Costs
Provision For UK Electricity Balancing Costs
Employee Benefits [Abstract]
Employee Benefits [Abstract]
Employee Benefits [Abstract]
Aggregate carrying value of the Group’s interests
Investments in subsidiaries, joint ventures and associates reported in separate financial statements
Net Debt [Table]
Net Debt [Table]
Net Debt [Table]
Plant and machinery
Machinery [member]
Profit before tax from continuing operations multiplied by UK corporation tax rate of 25% (2025: 25%; 2024: 25%)
Tax expense (income) at applicable tax rate
Retranslation of net assets offset by net investment hedge
Gains (Losses) On Exchange Differences On Translation, Net Of Net Investment Hedge, Before Tax
Gains (Losses) On Exchange Differences On Translation, Net Of Net Investment Hedge, Before Tax
-100 basis points change in discount rate
Discount Rate Risk, Fifty Basis Points Decrease [Member]
Discount Rate Risk, Fifty Basis Points Decrease [Member]
Investments held at FVOCI
Investments Held At FVTOCI [Member]
Investments held at FVTOCI [Member]
Hedge ratio
Hedge Ratio
Hedge Ratio
Eastern Green Link 4 Limited
Eastern Green Link 4 Limited [Member]
Eastern Green Link 4 Limited
Assets in the course of construction
Construction in progress [member]
Subsidiary Of Associate [Axis]
Subsidiary Of Associate [Axis]
Subsidiary Of Associate
Finance costs
Finance Cost [Abstract]
Finance Cost
Revenue from sale of goods and services, related party transactions
Revenue From Sale Of Goods And Rendering Of Services, Related Party Transactions
Revenue From Sale Of Goods And Rendering Of Services, Related Party Transactions
Interim dividend in respect of the current year
Interim Dividend In Respect Of Current Year [Member]
Interim Dividend in Respect of Current Year [Member]
Commodity contract derivatives
Commodity Derivatives, Netting [Member]
Commodity Derivatives, Netting
Amount of unclaimed dividends derecognised
Unclaimed Dividends Liability, Derecognition
Unclaimed Dividends Liability, Derecognition
Customer contributions
Current deposits from customers
Disposal groups classified as held for sale
Disposal groups classified as held for sale [member]
Current assets
Current
Current assets [abstract]
Commercial paper
Current commercial papers issued and current portion of non-current commercial papers issued
Schedule of significant changes in contract assets and contract liabilities
Explanation of significant changes in contract assets and contract liabilities [text block]
Other payables
Other current payables
Entity Address, Postal Zip Code
Entity Address, Postal Zip Code
Non-current assets
Non-current
Non-current assets [abstract]
Disclosure of reserves within equity [table]
Disclosure of reserves within equity [table]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Additions
Additions other than through business combinations, property, plant and equipment including right-of-use assets
Derivative financial assets
Derivative Financial Assets, Undiscounted Cash Flows
Derivative Financial Assets, Undiscounted Cash Flows
National Grid Ventures – US
National Grid Ventures - US [Member]
National Grid Ventures - US
Tax
Disclosure of income tax [text block]
Revenue
Description of accounting policy for recognition of revenue [text block]
Capital losses
Capital Losses [Member]
Capital Losses [Member]
Transaction fees related to Rights Issue
Transaction fees related to Rights Issue
Payments for share issue costs
Transformation programe, period
Transformation Programme, Period
Transformation Programme, Period
Schedule of trade and other receivables
Disclosure Of Trade And Other Receivables Explanatory [Table Text Block]
Disclosure Of Trade And Other Receivables Explanatory [Table Text Block]
Value of penalty as percentage of entity's turnover
Litigation, Maximum Penalty, Percentage Of Entity's Revenue
Litigation, Maximum Penalty, Percentage Of Entity's Revenue
Interest paid
Interest paid
Interest paid, classified as financing activities
Defined benefit plan costs:
Past service cost and gains (losses) arising from settlements, net defined benefit liability (asset) [abstract]
10% decrease in commodity prices
Sensitivity Analysis, 10 Percent Decrease In Commodity Prices
Sensitivity Analysis, 10 Percent Decrease In Commodity Prices
Energy Impact Fund LP
Energy Impact Fund LP [Member]
Energy Impact Fund LP [Member]
Shares reissued to employee share schemes as percent of ordinary shares
Shares Reissued To Employee Share Schemes As Percent Of Ordinary Shares
Shares Reissued To Employee Share Schemes As Percent Of Ordinary Shares
Software
Computer software [member]
Real discount rate (in percent)
Major Assumptions Made Concerning Future Events, Other Provisions, Discount Rate
Major Assumptions Made Concerning Future Events, Other Provisions, Discount Rate
Accounting policy choices
Disclosure of voluntary change in accounting policy [text block]
Interest (charges)/income
Increase (Decrease) Through Interest Expense (Income), Liabilities Arising From Financing Activities
Increase (Decrease) Through Interest Expense (Income), Liabilities Arising From Financing Activities
Unwinding of discount
Increase through adjustments arising from passage of time, other provisions
Reserves within equity [axis]
Reserves within equity [axis]
Insurance claim from loss of property, plant and equipment
Cash Flows Relating To Insurance Claim From Loss Of Property Plant And Equipment Investing Activities
Cash Flows Relating To Insurance Claim From Loss Of Property Plant And Equipment Investing Activities
UELs limited to 2060, impact on depreciation expense
Sensitivity Analysis, Useful Economic Life Limited To 2060, Impact On Depreciation Expense
Sensitivity Analysis, Useful Economic Life Limited To 2060, Impact On Depreciation Expense
Depreciation, amortisation and impairment
Depreciation, amortisation and impairment
Depreciation, amortisation and impairment loss (reversal of impairment loss) recognised in profit or loss
Disclosure of analysis of other comprehensive income by item [line items]
Disclosure of analysis of other comprehensive income by item [line items]
Related party transactions [abstract]
Related party transactions [abstract]
Cash flows from investing activities
Cash flows from (used in) investing activities [abstract]
Interest (charges)/income
Increase (Decrease) Through Interest Income (Expenses), Other Financing Derivatives
Increase (Decrease) Through Interest Income (Expenses), Other Financing Derivatives
Commodity price risk
Commodity price risk [member]
Reclassification to held for sale (note 10)
Decrease through classified as held for sale, property, plant and equipment including right-of-use assets
Employee contributions
Decrease (increase) in net defined benefit liability (asset) resulting from contributions to plan by plan participants
Interest In Other Entities [Axis]
Interest In Other Entities [Axis]
Interest In Other Entities
Dividends declared before financial statements authorised for issue (GBP per share)
Dividends proposed or declared before financial statements authorised for issue but not recognised as distribution to owners per share
Equity shareholders of the parent from discontinued operations
Comprehensive income from discontinued operations, attributable to owners of parent
Debt covenants, impacted companies
Debt Covenants, Impacted Companies
Debt Covenants, Impacted Companies
Transfer between reserves
Increase (decrease) through transfer to statutory reserve, equity
Schedule of tax charged to the consolidated income statement for continuing operations and components of tax expense
Disclosure Of Major Components Of Tax Expense (Income) [Table Text Block]
Disclosure Of Major Components Of Tax Expense (Income) [Table Text Block]
Cash and cash equivalents
Description of accounting policy for determining components of cash and cash equivalents [text block]
Facilities held as backup to commercial paper and similar borrowings
Facilities Held As Backup To Commercial Paper And Similar Borrowings [Member]
Facilities Held As Backup To Commercial Paper And Similar Borrowings [Member]
Share-based payments
Increase (decrease) through share-based payment transactions, equity
FVTPL investments
Current financial assets at fair value through profit or loss
Basic EPS (discontinuing) (in GBP per share)
Basic earnings (loss) per share from discontinued operations
Other payables
Other non-current payables
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Net investment hedges
Hedges of net investment in foreign operations [member]
Total non-current assets
Non-current assets
Non-current assets
Proportion of ownership interest in associate
Proportion of ownership interest in associate
Reconciliation of changes in other provisions [abstract]
Reconciliation of changes in other provisions [abstract]
Weighted average amortization period for contract liabilities
Revenue for Contract Liabilities, Weighted Average Amortisation Period
Revenue for Contract Liabilities, Weighted Average Amortisation Period
National Grid Renewables
National Grid Renewables [Member]
National Grid Renewables
Net cash inflow from operating activities – continuing operations
Cash flows from (used in) operating activities, continuing operations
Transmission
Transmission [Member]
Transmission [Member]
Disclosure of defined benefit plans [table]
Disclosure of defined benefit plans [table]
Classes of property, plant and equipment [axis]
Classes of property, plant and equipment [axis]
Schedule of other non-current assets
Disclosure Of Other Non Current Assets Explanatory [Table Text Block]
Disclosure Of Other Non Current Assets Explanatory [Table Text Block]
Bonds
Non-current portion of non-current bonds issued
Cash-generating units [axis]
Cash-generating units [axis]
Classes of property, plant and equipment [domain]
Classes of property, plant and equipment [domain]
Actuarial assumptions [domain]
Actuarial assumptions [domain]
Entity Address, Country
Entity Address, Country
Number of security arrangements
Number Of Defined Benefit Plans with Security Arrangements
Number Of Defined Benefit Plans with Security Arrangements
Increase in actuarial assumption, percent
Percentage Of Reasonably Possible Increase In Actuarial Assumption, Percent
Percentage Of Reasonably Possible Increase In Actuarial Assumption, Percent
Euro
Euro Member Countries, Euro
Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract]
Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract]
Gas plant – storage
Gas Plant - Storage [Member]
Gas Plant - Storage [Member]
Disclosure of reconciliation of changes in intangible assets and goodwill [line items]
Disclosure of reconciliation of changes in intangible assets and goodwill [line items]
Accrued income
Unbilled Revenue [Member]
Unbilled Revenue [Member]
Exchange movements
Foreign exchange movements
Effect of exchange rate changes on cash and cash equivalents
Interest received
Interest received
Interest received, classified as investing activities
Discount rate – past service
Actuarial Assumption Of Discount Rates, Past Service
Actuarial Assumption Of Discount Rates, Past Service
Foreign currencies
Description of accounting policy for foreign currency translation [text block]
Remaining performance obligation, expected timing of satisfaction, period
Revenue, Remaining Performance Obligation, Expected Timing Of Satisfaction, Period
Revenue, Remaining Performance Obligation, Expected Timing Of Satisfaction, Period
Document Annual Report
Document Annual Report
Entities [Table]
Entities [Table]
Return on plan assets (less than)/in excess of interest
Decrease (increase) in net defined benefit liability (asset) resulting from return on plan assets excluding interest income or expense
Basic earnings from discontinued operations
Profit (loss) from discontinued operations attributable to ordinary equity holders of parent entity, used in calculating basic earnings per share
Contract liabilities
Non-current
Non-current contract liabilities
Disclosure of detailed information about financial instruments [table]
Disclosure of detailed information about financial instruments [table]
Number of defined benefit plans
Number Of Defined Benefit Plans
Number Of Defined Benefit Plans
Geographical areas [domain]
Geographical areas [domain]
-20 basis points decrease between RPI and CPI
Sensitivity Analysis, 20 Basis Point Change Decrease Between Retail Price Index And Consumer Price Index
Sensitivity Analysis, 20 Basis Point Change Decrease Between Retail Price Index And Consumer Price Index
Disposals
Increase (decrease) through loss of control of subsidiary, deferred tax liability (asset)
Other non-current assets
Disclosure of other non-current assets [text block]
Trade and other receivables
Trade and other receivables
Trade and other current receivables
Financial risk management
Sensitivities
Disclosure of financial risk management [text block]
Schedule of changes in net debt
Analysis Of Changes In Net Debt [Table Text Block]
Analysis Of Changes In Net Debt [Table Text Block]
Entity Interactive Data Current
Entity Interactive Data Current
Maine Yankee Atomic Power Company
Maine Yankee Atomic Power Company [Member]
Maine Yankee Atomic Power Company [Member]
FFO/adjusted net debt
Funds From Operations Ratio
Funds From Operations Ratio
SOFR
Secured Overnight Financing Rate - SOFR [Member]
Secured Overnight Financing Rate - SOFR
Levels of fair value hierarchy [axis]
Levels of fair value hierarchy [axis]
Consideration paid (received)
Total consideration
Consideration paid (received)
Total shareholders’ equity
Equity attributable to owners of parent [member]
Scrip dividend
Scrip Dividends-Related Share Issue Recognized
Scrip Dividends-Related Share Issue Recognized
Finance costs
Finance costs
Finance costs
Schedule of financial assets
Disclosure of financial assets [text block]
Number of equity investments
Number Of Equity Investments
Number Of Equity Investments
A Ordinary shares
A Ordinary Shares [Member]
A Ordinary Shares [Member]
Actuarial assumption of life expectancy after retirement
Actuarial assumption of life expectancy after retirement [member]
Dividends [Axis]
Dividends Distribution [Axis]
Dividends Distribution [Axis]
Disclosure of credit risk exposure [table]
Disclosure of credit risk exposure [table]
Basis of preparation and recent accounting developments
Disclosure of material accounting policy information [text block]
Fair value gains and losses
Increase (Decrease) Through Changes In Fair Values, Financial Investments
Increase (Decrease) Through Changes In Fair Values, Financial Investments
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption
Other liabilities
Other liabilities
Pensions
Pension defined benefit plans [member]
Net debt
Description Of Accounting Policy For Net Debt [Policy Text Block]
Description of Accounting Policy For Net Debt [Policy Text Block]
Reconciliation of changes in allowance account for credit losses of financial assets [abstract]
Reconciliation of changes in allowance account for credit losses of financial assets [abstract]
Gross amounts offset
Gross amounts offset
Gross financial liabilities set off against financial assets subject to offsetting, enforceable master netting arrangements or similar agreements
Equity investments in joint ventures and associates
Investments accounted for using equity method [member]
Net debt to RAV gearing covenants
Debt Covenants, Net Debt To RAV Gearing Ratio
Debt Covenants, Net Debt To RAV Gearing Ratio
Net gains (losses) in respect of cash flow hedging of capital expenditure
Gains (losses) on cash flow hedges, net of tax
Provision for impairment of receivables, period
Provision For Impairment Of Receivables, Period
Provision For Impairment Of Receivables, Period
Cash outflows on derivatives
Cash outflows on derivatives
Payments For Derivatives Contracts, Classified As Financing Activities
Payments For Derivatives Contracts, Classified As Financing Activities
Remeasurement gains/(losses) on pension assets and post-retirement benefit obligations
Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans
Government securities
Government Securities [Member]
Government Securities [Member]
Remeasurements of pension assets and post-retirement benefit obligations
Income tax relating to remeasurements of defined benefit plans included in other comprehensive income
Total deferred tax from continuing operations
Deferred Tax Expense (Income) And Adjustments For Deferred Tax Of Prior Periods
Deferred Tax Expense (Income) And Adjustments For Deferred Tax Of Prior Periods
Entity Central Index Key
Entity Central Index Key
Disclosure of aggregate information of associates and joint venture
Disclosure Of Aggregate Information Of Associates And Joint Venture Not Individually Material [Table Text Block]
Disclosure Of Aggregate Information Of Associates And Joint Venture Not Individually Material
Total items from continuing operations that may be reclassified subsequently to profit or loss
Other comprehensive income that will be reclassified to profit or loss, net of tax
Cash and cash equivalents
Disclosure of cash and cash equivalents [text block]
Merger
Merger reserve [member]
Dividends received on equities held at fair value through other comprehensive income (FVOCI)
Dividends recognised for investments in equity instruments designated at fair value through other comprehensive income, held at end of reporting period
Reconciliation of changes in deferred tax liability (asset) [abstract]
Reconciliation of changes in deferred tax liability (asset) [abstract]
Hedge ineffectiveness
Gain (loss) on hedge ineffectiveness
Basic EPS
Basic earnings per share [abstract]
Attributable to:
Profit (loss), attributable to [abstract]
Risk exposure associated with instruments sharing characteristic
Risk exposure associated with instruments sharing characteristic
Net (losses)/gains in respect of cash flow hedges
Net gains in respect of cash flow hedges
Gains (losses) on cash flow hedges, before tax
Net interest (expense)/income
Interest income (expense)
Entity Filer Category
Entity Filer Category
Share-based payments
Current tax relating to items credited (charged) directly to equity
C Ordinary shares
C Ordinary Shares [Member]
C Ordinary Shares [Member]
Derivatives not designated as hedges for hedge accounting
Loss On Derivative Financial Instruments Not Designated As Hedges
Loss On Derivative Financial Instruments Not Designated As Hedges
Triple ‘A’ range institutions and non-G7 sovereign entities (AAA)
AAA Institutions And Non-G7 Sovereign Entities [Member]
AAA Institutions and Non-G7 Sovereign Entities [Member]
Interest cost
Interest income
Increase (decrease) in net defined benefit liability (asset) resulting from interest expense (income)
Major loan agreement
Major Loan Agreement [Member]
Major Loan Agreement
+10% change in venture capital price
Venture Capital Price, Ten Percent Increase [Member]
Venture Capital Price, Ten Percent Increase
Foreign exchange forward contracts
Financing Derivatives - Foreign Exchange Forward Contracts [Member]
Financing Derivatives - Foreign Exchange Forward Contracts [Member]
Classes of ordinary shares [domain]
Classes of ordinary shares [domain]
Net cash inflow from investing activities – discontinued operations
Cash flows from (used in) investing activities, discontinued operations
Hedging instrument notional
Nominal amount of hedging instrument
Operating profit
Total operating profit from continuing operations
Operating profit from continuing operations
Operating profit
Profit (loss) from operating activities
Disposal Group, Name [Domain]
Disposal Group, Name [Domain]
Disposal Group, Name [Domain]
Other receivables
Other current receivables
Defined benefit plan, buy-in-transaction
Defined Benefit Plan, Buy-In-Transaction
Defined Benefit Plan, Buy-In-Transaction
Tax
Income Tax Components, Other Reserves
Income Tax Components, Other Reserves
Audit fees payable to the Parent Company’s auditors and their associates
Auditor's remuneration for audit services
Entity Address, Address Line One
Entity Address, Address Line One
Gas distribution
Gas Distribution Assets [Member]
Gas Distribution Assets
UK Electricity System Operator
UK Electricity System Operator [Member]
UK Electricity System Operator
Share of total comprehensive income
Share of total comprehensive income of associates and joint ventures accounted for using equity method
Discontinued operations
Discontinued operations [member]
Defined benefit pension costs
Post-Employment Benefit Expense Defined Benefit Plans, Pension Plans
Post-Employment Benefit Expense Defined Benefit Plans, Pension Plans
Changes in pensions and other post-retirement benefit obligations
Adjustments for increase (decrease) in employee benefit liabilities
Included within finance income and costs
Pensions And Other Post-Retirement Benefits, Finance Income And Costs [Abstract]
Pensions And Other Post-retirement Benefits, Finance Income And Costs [Abstract]
Increase (Decrease) in Contract Liabilities [Roll Forward]
Increase (Decrease) In Contract Liabilities [Roll Forward]
Increase (Decrease) in Contract Liabilities [Roll Forward]
Trade and other receivables
Trade and Other Receivables [Member]
Trade and Other Receivables [Member]
American Depositary Shares
American Depositary Shares [Member]
American Depositary Shares
Ofgem’s investigation, North Hyde Substation incident
Ofgem’s Investigation, North Hyde Substation Incident [Member]
Ofgem’s Investigation, North Hyde Substation Incident
+10% change in venture capital price
Sensitivity Analysis, 10 Percent Increase In Venture Capital Price
Sensitivity Analysis, 10 Percent Increase In Venture Capital Price
Clean Line Energy Partners LLC
Clean Line Energy Partners LLC [Member]
Clean Line Energy Partners LLC [Member]
Analysis of total exceptional items and remeasurements after tax
Analysis Of Exceptional Items And Remeasurements After Tax [Abstract]
Analysis Of Exceptional Items And Remeasurements After Tax
Financing derivatives
Financing Derivatives
Financing Derivatives
Expected contributions to plans in the following year
Estimate of contributions expected to be paid to plan for next annual reporting period
Liability for emission provisions
Liability For Emission Provisions [Member]
Liability For Emission Provisions
10% decrease in commodity prices
Commodity Price Risk, Ten Percent Decrease [Member]
Commodity Price Risk, Ten Percent Decrease [Member]
Provisions
Disclosure of provisions [text block]
Statement of cash flows [abstract]
Statement of cash flows [abstract]
Disclosure of financial assets [table]
Disclosure of financial assets [table]
Other movements in non-controlling interests
Increase (Decrease) Though Other Movements In Non-Controlling Interests, Equity
Increase (Decrease) Though Other Movements In Non-Controlling Interests, Equity
Restructuring Activities [Axis]
Restructuring Activities [Axis]
Restructuring Activities
Diversified alternatives
Investment funds, amount contributed to fair value of plan assets
Active members
Active Members [Member]
Active Members [Member]
Unwinding of discount on provisions and other payables
Expense arising from passage of time on other provisions
Funding arrangements of defined benefit plans [domain]
Funding arrangements of defined benefit plans [domain]
Corporate tax adjustment in respect of prior years
Adjustments for current tax of prior periods
Cash collateral received/ pledged
Cash Collateral Pledged Subject To Enforceable Master Netting Agreement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities)
Cash Collateral Pledged Subject To Enforceable Master Netting Agreement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities)
Actuarial gains (losses) arising from changes in demographic assumptions, net of tax, defined benefit plans
Actuarial gains (losses) arising from changes in demographic assumptions, net of tax, defined benefit plans
Actuarial gains (losses) arising from changes in demographic assumptions, net of tax, defined benefit plans
Assumed US healthcare cost trend rates change
Actuarial assumption of medical cost trend rates [member]
Counterparty Name [Domain]
Counterparty Name [Domain]
Retail customer receivables
Retail Customer Receivables [Member]
Retail Customer Receivables [Member]
Medicare subsidy received
Increase (Decrease) In Net Defined Benefit Liability (Asset) Resulting From Medical Subsidy Received
Increase (Decrease) In Net Defined Benefit Liability (Asset) Resulting From Medical Subsidy Received
Total (income)/expense included in income statement
Post-employment benefit expense in profit or loss, defined benefit plans
Adjustment in respect of foreign tax rates
Tax effect of foreign tax rates
National Grid North America Inc.
National Grid North America Inc. [Member]
National Grid North America Inc.
Hedged items [axis]
Hedged items [axis]
Cash inflows relating to insurance recovery
Cash Inflows Relating To Insurance Recovery
Cash Inflows Relating To Insurance Recovery
Cash inflows on derivatives
Cash inflows on derivatives
Proceeds From Derivatives Contracts, Classified As Financing Activities
Proceeds From Derivatives Contracts, Classified As Financing Activities
-10% market area price change
Sensitivity Analysis, 10 Percent Decrease In Market Area Price Change
Sensitivity Analysis, 10 Percent Decrease In Market Area Price Change
Schedule of assets and liabilities classified as held for sale
Disclosure Of Assets And Liabilities Classified As Held For Sale Explanatory [Table Text Block]
Disclosure Of Assets And Liabilities Classified As Held For Sale Explanatory
UK Electricity Distribution Group
UK Electricity Distribution Group [Member]
UK Electricity Distribution Group
Current
Current Derivative [Member]
Current Derivative Financial Assets [Member]
Current liabilities
Current liabilities [abstract]
Characteristics of defined benefit plans [domain]
Characteristics of defined benefit plans [domain]
Electricity capacity
Commodity Derivatives - Electricity Capacity [Member]
Commodity Derivatives - Electricity Capacity [Member]
Schedule of components of net debt
Schedule Of Components Of Net Debt [Table Text Block]
Schedule Of Components Of Net Debt [Table Text Block]
Investments in joint ventures and associates
Investments accounted for using equity method, beginning balance
Investments accounted for using equity method, ending balance
Investments accounted for using equity method
UK
Domestic Tax Authority [Member]
Domestic Tax Authority [Member]
Disclosure of financial instruments by type of interest rate [table]
Disclosure of financial instruments by type of interest rate [table]
Income/(cost) recognised in the income statement before adjustment for irrecoverable surplus
Increase (decrease) in net defined benefit liability (asset) resulting from expense (income) in profit or loss
Disclosure of transactions between related parties [line items]
Disclosure of transactions between related parties [line items]
Proceeds
Portion of consideration paid (received) consisting of cash and cash equivalents
Other comprehensive income from continuing operations
Other comprehensive (loss)/income from discontinued operations
Other comprehensive income [abstract]
Disclosure of detailed information about hedging instruments [line items]
Disclosure of detailed information about hedging instruments [line items]
Cash flow hedges, cost of hedging and own credit reserve
Income tax relating to cash flow hedges included in other comprehensive income
UK Electricity Distribution DNO
UK Electricity Distribution DNOs [Member]
UK Electricity Distribution DNOs
Proportion of ownership interest in joint operation
Proportion of ownership interest in joint operation
-10% market area price change
Market Area Price Risk, Ten Percent Decrease [Member]
Market Area Price Risk, Ten Percent Decrease
Trading losses
Trading Losses [Member]
Trading Losses [Member]
Other provisions [abstract]
Classes of share capital [domain]
Classes of share capital [domain]
+20 basis points increase between RPI and Consumer Price Index (CPI)
Sensitivity Analysis, 20 Basis Point Change Increase Between Retail Price Index And Consumer Price Index
Sensitivity Analysis, 20 Basis Point Change Increase Between Retail Price Index And Consumer Price Index
Other non-audit services not covered above
Auditor's Remuneration For Other Services, Other Non Audit Services Not Covered Above
Auditor's Remuneration For Other Services, Other Non Audit Services Not Covered Above
Deferred tax adjustment in respect of prior years
Adjustments for deferred tax of prior periods
Assumed life expectations for a retiree age 65 today: Females
Actuarial Assumption Of Life Expectancy After Retirement, Female
Actuarial Assumption Of Life Expectancy After Retirement, Female
Salary increases
Actuarial assumption of expected rates of salary increases
Cost efficiency programme
Cost efficiency programme
Expense Of Restructuring Activities, Cost Efficiency Programme
Expense Of Restructuring Activities, Cost Efficiency Programme
Proceeds of Rights Issue
Proceeds from issue of ordinary shares
Investments in joint ventures and associates
Purchase of interests in investments accounted for using equity method
Finance income
Finance income
Finance income
Classes of financial liabilities [axis]
Classes of financial liabilities [axis]
All other fees:
Other Auditor Remuneration [Abstract]
Other Auditor Remuneration
Disclosure of inventories
Disclosure Of Inventories [Table Text Block]
Disclosure Of Inventories
Classes of financial liabilities [domain]
Classes of financial liabilities [domain]
Document Shell Company Report
Document Shell Company Report
Non-derivative financial liabilities
Disclosure of maturity analysis for non-derivative financial liabilities [abstract]
Borrowings, adjustment to interest rate basis
Borrowings, adjustment to interest rate basis
Investments at fair value through other comprehensive income
Income tax relating to investments in equity instruments included in other comprehensive income
Deferred income
Non-Current Deferred Income
Non-Current Deferred Income
Disclosure of trade and other receivables [line items]
Disclosure of other provisions [line items]
Disclosure of other provisions [line items]
Additions
Additions to right-of-use assets
Trade receivables and accrued income, net
Trade receivables and accrued income, net
Trade Receivables And Accrued Income, Net
Trade Receivables And Accrued Income, Net
Decrease (increase) in net defined benefit liability (asset) resulting from resulting from contributions to plan by employer
Employer contributions
Decrease (increase) in net defined benefit liability (asset) resulting from resulting from contributions to plan by employer
Contributions to National Grid Renewables and Emerald Energy Venture LLC
Cash flows used in obtaining control of subsidiaries or other businesses, classified as investing activities
Inflation, UK RPI change
Other price risk [member]
Average number of employees
Average number of employees
Other services supplied
Auditor's Remuneration For Audit Services, Other Audit Services
Auditor's Remuneration For Audit Services, Other Audit Services
Plan assets
Plan assets [member]
Net amount
Net Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements
Net Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements
Customer contributions
Non-current deposits from customers
Balance in cash flow hedge reserve, Continuing hedges
Reserve of cash flow hedges, continuing hedges
Cost of hedging
Reserve Of Cost Of Hedging [Member]
Reserve Of Cost Of Hedging [Member]
Lease liabilities
Lease liabilities
Disclosure of financial assets [abstract]
Disclosure of financial assets [abstract]
Derivatives designated as hedges for hedge accounting
Loss On Derivative Financial Instruments Designated As Hedges
Loss On Derivative Financial Instruments Designated As Hedges
Transactions in own shares
Increase (decrease) through treasury share transactions, equity
Receivables due from joint ventures
Receivables due from joint ventures
Other non-cash movements
Increase (decrease) through other changes, liabilities arising from financing activities
Balance in cash flow hedge reserve, Discontinued hedges
Reserve of cash flow hedges, hedging relationships for which hedge accounting is no longer applied
Investments accounted for using equity method [abstract]
Investments accounted for using equity method [abstract]
Discount rate – future service
Actuarial Assumption Of Discount Rates, Future Service
Actuarial Assumption Of Discount Rates, Future Service
Scrip dividend-related share issue
Issued during the year in lieu of dividends
Scrip Dividends-Related Share Issue Recognized As Distributions To Owners
Scrip Dividends-Related Share Issue Recognized As Distributions To Owners
Inflation-linked swaps
Financing Derivatives - Inflation Linked Swaps [Member]
Financing Derivatives - Inflation Linked Swaps [Member]
Net debt
Increase (Decrease) In Net Debt [Roll Forward]
Increase (Decrease) In Net Debt [Roll Forward]
Minimum
Minimum [Member]
Profit after tax from continuing operations
Profit after tax from continuing operations
Profit (loss) from continuing operations
Liabilities arising from financing activities [domain]
Liabilities arising from financing activities [domain]
Interest rate swaps
Financing Derivatives - Interest Rate Swaps [Member]
Financing Derivatives - Interest Rate Swaps [Member]
Reclassifications
Increase (decrease) through transfers, intangible assets other than goodwill
Capital redemption
Capital redemption reserve [member]
Trade and other receivables
Description of accounting policy for trade and other receivables [text block]
Diluted total earnings
Profit (loss), attributable to ordinary equity holders of parent entity, used in calculating diluted earnings per share
Triple ‘A’ vehicles (AAA)
AAA Investment Vehicles [Member]
AAA Investment Vehicles [Member]
Share capital
Issued capital
Financial instruments
Financial instruments subject to enforceable master netting arrangement or similar agreement not set off against financial liabilities
Deferred tax assets not recognised
Unused tax losses for which no deferred tax asset recognised
Balance in translation reserve, Discontinued hedges
Reserve of exchange differences on translation, hedging relationships for which hedge accounting is no longer applied
Exchange adjustments and other
Increase (decrease) through net exchange differences, deferred tax liability (asset)
Number of shares held in joint venture (in shares)
Number Of Shares Held In Associates
Number Of Shares Held In Associates
Other borrowings
Interest Expense On Other Borrowings, Including Capitalised
Interest Expense On Other Borrowings, Including Capitalised
Exceptional Items And Remeasurements [Abstract]
Exceptional Items And Remeasurements [Abstract]
Exceptional Items And Remeasurements [Abstract]
Reconciliation of changes in goodwill [abstract]
Reconciliation of changes in goodwill [abstract]
Products and services [axis]
Products and services [axis]
Other provisions
Other provisions, beginning balance
Other provisions, ending balance
Other provisions
Discounted
Other provisions
Liabilities
Financial liabilities
Other net temporary differences
Other temporary differences [member]
Exchange losses
Other Comprehensive Income, Net Of Tax, Gains (Losses) Through Foreign Exchange Rates, Defined Benefit Plans
Other Comprehensive Income, Net Of Tax, Gains (Losses) Through Foreign Exchange Rates, Defined Benefit Plans
Disclosure of reserves within equity [line items]
Disclosure of reserves within equity [line items]
Tax
Tax on exceptional items and remeasurements
Total tax charge from continuing operations
Tax expense (income)
Yankee Atomic Electric Company
Yankee Atomic Electric Company [Member]
Yankee Atomic Electric Company [Member]
Cash-generating units [domain]
Cash-generating units [domain]
Post balance sheet events
Disclosure of events after reporting period [text block]
Number of employees, year end
Number of employees
Document Transition Report
Document Transition Report
Trade and other receivables
Trade and other receivables
Cash flows from operating activities
Cash flows from (used in) operating activities [abstract]
Schedule of statements for discontinued operations
Disclosure of analysis of single amount of discontinued operations [text block]
Share of post-tax results of joint ventures and associates
Share of profit (loss) of associates and joint ventures accounted for using equity method
Other non-current liabilities
Disclosure of other non-current liabilities [text block]
Disclosure of defined benefit plans [line items]
Disclosure of defined benefit plans [line items]
Document Period End Date
Document Period End Date
Non-adjusting events after reporting period [member]
Non-adjusting events after reporting period [domain]
Disclosure of classes of share capital [line items]
Disclosure of classes of share capital [line items]
Exchange adjustments
Increase (decrease) through net exchange differences, right-of-use assets
Exceptional items and remeasurements
Disclosure Of Exceptional Items And Remeasurements [Text Block]
Disclosure Of Exceptional items And Remeasurements [Text Block]
Deferred payables
Current deferred income other than current contract liabilities
Goodwill
Disclosure of goodwill [text block]
Maturity [axis]
Maturity [axis]
Cash inflows on derivatives
Cash inflows on derivatives
Cash receipts from futures contracts, forward contracts, option contracts and swap contracts, classified as investing activities
Tax on items that may be reclassified subsequently to profit or loss
Tax on items that may be reclassified subsequently to profit or loss
Income tax relating to components of other comprehensive income that will be reclassified to profit or loss
UK
UNITED KINGDOM
Issue of treasury shares
Sale or issue of treasury shares
Share-based payments
Deferred tax relating to items credited (charged) directly to equity
Classes of financial instruments [axis]
Classes of financial instruments [axis]
Goodwill
Goodwill
Goodwill at beginning of period
Goodwill at end of period
Goodwill
Associates [axis]
Associates [axis]
Total tax relating to share-based payments recognised directly in equity from continuing operations
Current and deferred tax relating to items credited (charged) directly to equity
Document Type
Document Type
Other than by instalments
Borrowings Paid By Other Than Instalments [Member]
Borrowings Paid By Other Than Instalments [Member]
Share-based payments
Expense from share-based payment transactions with employees
Net movements in short-term financial investments
Net movements in short-term financial investments
Cash flows from (used in) decrease (increase) in short-term deposits and investments
Rate of increase in RPI – future service
Actuarial Assumption Of Expected Rates Of Pension Increases, Future Service
Actuarial Assumption Of Expected Rates Of Pension Increases, Future Service
Assets (Liabilities)
Net Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements [Abstract]
Net Financial Assets (Liabilities) Subject to Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements [Abstract]
FVOCI debt
Reserve of gains and losses on financial assets measured at fair value through other comprehensive income [member]
Classes of financial assets [axis]
Classes of financial assets [axis]
Gross lease liabilities
Lease liabilities
Gross lease liabilities
Other short term differences
Temporary Differences, Other Short Term Differences [Member]
Temporary Differences, Other Short Term Differences
Group’s share of post-tax results for the year
Share of profit (loss) of joint ventures accounted for using equity method
Exchange adjustments
Increase (decrease) through net exchange differences, intangible assets other than goodwill
Profit or loss [abstract]
Profit or loss [abstract]
Reclassification adjustments on hedging instruments, before tax
Reclassification Adjustments on Hedging Instruments, Before Tax
Reclassification Adjustments on Hedging Instruments, Before Tax
Contract liabilities
Current
Current contract liabilities
Gas plant – meters
Gas Plant - Meters [Member]
Gas Plant - Meters [Member]
Statistical Measurement [Axis]
Statistical Measurement [Axis]
Operating costs from continuing operations include:
Operating Cost [Abstract]
Operating Cost
Disclosure of tax (credited)/charged to the consolidated statement of comprehensive income and equity
Disclosure Of Income Tax Relating To Components Of Other Comprehensive Income And Items Credited (Charged) Directly To Equity [Table Text Block]
Disclosure Of Income Tax Relating To Components Of Other Comprehensive Income And Items Credited (Charged) Directly To Equity [Table Text Block]
Interest (charges)/income
Increase (Decrease) Through Interest Income (Expenses), Net Debt
Increase (Decrease) Through Interest Income (Expenses), Net Debt
Derivative financial instruments
Derivative Financial Instruments [Member]
Derivative Financial Instruments [Member]
UK Gas Transmission business
UK Gas Transmission [Member]
UK Gas Transmission [Member]
Reclassification to held for sale
Increase (Decrease) In Financial Investments Through Reclassification To Held For Sale And Discontinued Operations
Increase (Decrease) In Financial Investments Through Reclassification To Held For Sale And Discontinued Operations
Classes of assets [axis]
Classes of assets [axis]
Included within operating costs
Pensions And Other Post-Retirement Benefits, Operating Costs [Abstract]
Pensions And Other Post-retirement Benefits, Operating Costs [Abstract]
Operating segments
Operating segments [member]
Disclosure of joint operations [line items]
Disclosure of joint operations [line items]
In 4 to 5 years
Later than four years and not later than five years [member]
Direct Global Power, Inc.
Direct Global Power, Inc. [Member]
Direct Global Power, Inc. [Member]
Disclosure of reconciliation of changes in goodwill [table]
Disclosure of reconciliation of changes in goodwill [table]
Related amounts available to be offset but not offset in statement of financial position
Amounts subject to enforceable master netting arrangement or similar agreement not set off against financial liabilities [abstract]
National Gas Transmission Plc
National Gas Transmission Plc [Member]
National Gas Transmission Plc
Total shareholders’ equity
Equity attributable to owners of parent
Derivative cash flows included in revenue
Increase (Decrease) Through Derivative Cash Flows Included In Revenue, Net Debt
Increase (Decrease) Through Derivative Cash Flows Included In Revenue, Net Debt
Earnings per share [abstract]
Earnings per share [abstract]
Range [axis]
Range [axis]
Change in risk variable, impact on income statement
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Earnings
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Earnings
Components of equity [axis]
Components of equity [axis]
Fixed rate
Fixed interest rate [member]
Schedule of effective tax rate reconciliation
Disclosure Of Reconciliation Of Accounting Profit Multiplied By Applicable Tax Rates And Average Effective Tax Rate [Table Text Block]
Disclosure Of Reconciliation Of Accounting Profit Multiplied By Applicable Tax Rates And Average Effective Tax Rate [Table Text Block]
Net cash flow used in financing activities – discontinued operations
Cash flows from (used in) financing activities, discontinued operations
Entity Information [Line Items]
Entity Information [Line Items]
Exchange adjustments
Increase (Decrease) Through Net Exchange Differences, Investments Accounted For Using Equity Method
Increase (Decrease) Through Net Exchange Differences, Investments Accounted For Using Equity Method
Profit before tax
Profit before tax from continuing operations
Profit before tax
Profit (loss) before tax
Phone Fax Number Description
Phone Fax Number Description
Decrease in risk variable, impact on earnings
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Decrease In Risk Variable, Impact On Earnings
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Decrease In Risk Variable, Impact On Earnings
Disposal of interests in the UK Electricity System Operator, UK Gas Transmission business, The Narragansett Electric Company and Millennium Pipeline Company LLC
Cash flows from losing control of subsidiaries or other businesses, classified as investing activities
Double ‘A’ range institutions (AA)
AA Institutions [Member]
AA Institutions [Member]
Decrease in risk variable, impact on net assets
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Decrease In Risk Variable, Impact On Net Assets
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Decrease In Risk Variable, Impact On Net Assets
Disclosure of financial instruments by type of interest rate
Disclosure of financial instruments by type of interest rate [text block]
Other equity reserves
Disclosure of share capital, reserves and other equity interest [text block]
GasT TopCo Limited
GasT TopCo Limited [Member]
GasT TopCo Limited
Actuarial (losses)/gains – experience
Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from experience adjustments
UELs limited to 2050, impact on depreciation expense
Sensitivity Analysis, Useful Economic Life Limited To 2050, Impact On Depreciation Expense
Sensitivity Analysis, Useful Economic Life Limited To 2050, Impact On Depreciation Expense
Categories of related parties [domain]
Categories of related parties [domain]
Number of ordinary shares per ADS (in shares)
Number Of Ordinary Shares Per ADS
Number Of Ordinary Shares Per ADS
Total for all joint ventures
Total for all joint ventures [member]
Disclosure of disaggregation of revenue from contracts with customers [abstract]
Disclosure of other provisions [table]
Disclosure of other provisions [table]
Provisions
Non-current
Other non-current provisions
Schedule of finance income and costs
Disclosure Of Finance Income And Costs Explanatory [Table Text Block]
Disclosure Of Finance Income And Costs Explanatory [Table Text Block]
Letter of credit
Investments, Letter Of Credit [Member]
Investments, Letter Of Credit
Classes of financial instruments [domain]
Classes of financial instruments [domain]
Exchange adjustments
Increase (decrease) through net exchange differences, property, plant and equipment including right-of-use assets
Auditor Location
Auditor Location
Financing derivatives
Financing Derivatives [Member]
Financing Derivatives [Member]
Dividends received
Dividends received from investments accounted for using equity method, classified as investing activities
Disclosure of subsidiaries taking advantage of audit exemption under section 479A of Companies Act 2006
Disclosure Of Entities Taking Advantage Of Audit Exemption Under Section 479A Of Companies Act 2006 [Table Text Block]
Disclosure Of Entities Taking Advantage Of Audit Exemption Under Section 479A Of Companies Act 2006
$864.9 million, 10-year loan
$864.9 Million, 10-Year Loan [Member]
$864.9 Million, 10-Year Loan
Cash and cash equivalents at start of year
Cash and cash equivalents at end of year
Cash and cash equivalents if different from statement of financial position
Tax charged/(credited) to other comprehensive income and equity
Income Tax Relating To Components Of Other Comprehensive Income And Items Credited (Charged) Directly To Equity
Income Tax Relating To Components Of Other Comprehensive Income And Items Credited (Charged) Directly To Equity
Products and services [domain]
Products and services [domain]
Schedule of main activities, revenue, operating profit and capital investment by operating segments
Disclosure of operating segments [text block]
Weighted average number of shares – basic (in shares)
Weighted average number of shares – basic (in shares)
Weighted average number of ordinary shares used in calculating basic earnings per share
Other investments
Restricted Balances, Other Investments [Member]
Restricted Balances - Other [Member]
Schedule of trade and other payables
Disclosure Of Trade And Other Payables Explanatory [Table Text Block]
Disclosure Of Trade And Other Payables Explanatory [Table Text Block]
Sheet Road Management Company Limited
Sheet Road Management Company Limited [Member]
Sheet Road Management Company Limited
Other Sensitivities [Domain]
Other Sensitivities [Domain]
[Domain] for Other Sensitivities [Axis]
Schedule of tax included within the statement of financial position and deferred tax assets not recognised
Disclosure of temporary difference, unused tax losses and unused tax credits [text block]
Net gains/(losses) taken to equity
Net Gains (Losses) Taken To Equity, Before Tax
Net Gains (Losses) Taken To Equity, Before Tax
Disclosure of detailed information about intangible assets [table]
Disclosure of detailed information about intangible assets [table]
Other equity reserves
Other equity reserves, beginning balance
Other equity reserves, ending balance
Other equity reserves – cost of hedging balances
Other reserves
Share-based payments
Key management personnel compensation, share-based payment
Borrowings
Total borrowings
Borrowings
Borrowings
Borrowings
Net gains on financial assets at fair value through profit and loss
Net gains on FVTPL financial assets
Gains (losses) on financial assets at fair value through profit or loss
Entity Well-known Seasoned Issuer
Entity Well-known Seasoned Issuer
Fixed interest rate bonds
Fixed Interest Rate Bonds [Member]
Fixed Interest Rate Bonds [Member]
National Grid Electricity Transmission plc
National Grid Electricity Transmission plc [Member]
National Grid Electricity Transmission plc [Member]
Other financial assets
Other financial assets
Auditor Information [Abstract]
Auditor Information
UK
Country of domicile [member]
Derivative contracts – receipts
Financing Derivatives - Receipts [Member]
Financing Derivatives - Receipts [Member]
Government securities and liability-driven investments
Government Securities And Liability-Driven Investments [Member]
Government Securities And Liability-Driven Investments
Counterparties [axis]
Counterparties [axis]
Other post-retirement benefits
Post-employment medical defined benefit plans [member]
Type of member [Domain]
Type Of Member [Domain]
[Domain] for Type Of Member [Axis]
Earnings per share (EPS)
Description of accounting policy for earnings per share [text block]
By instalments
Borrowings Paid By Instalments [Member]
Borrowings Paid By Instalments [Member]
Fair value hedges
Fair value hedges [member]
Number of plans showing funding shortfall
Defined Benefit Plan, Deficit, Number Of Plans
Defined Benefit Plan, Deficit, Number Of Plans
Disclosure of nature and extent of risks arising from financial instruments
Schedule of sensitivities on areas of estimation uncertainty and on financial instruments
Disclosure of nature and extent of risks arising from financial instruments [text block]
Other Sensitivities [Axis]
Other Sensitivities [Axis]
Other Sensitivities [Axis]
Financial and other investments
Description of accounting policy for financial assets [text block]
Entity Current Reporting Status
Entity Current Reporting Status
Fair value of plan assets
Fair value of plan assets
Plan assets, at fair value
Treasury shares, nominal value
Treasury shares
Net gain on the sale of the ESO
Gain (Loss) Recognised On Measurement To Fair Value Less Costs To Sell Or On Disposal Of Assets Or Disposal Groups
Gain (Loss) Recognised On Measurement To Fair Value Less Costs To Sell Or On Disposal Of Assets Or Disposal Groups
Derivative financial assets
Disclosure Of Maturity Analysis For Derivative Financial Assets [Abstract]
Disclosure Of Maturity Analysis For Derivative Financial Assets [Abstract]
Rate of increase in RPI – past service
Actuarial Assumption Of Expected Rates Of Pension Increases, Past Service
Actuarial Assumption Of Expected Rates Of Pension Increases, Past Service
Pensioner members
Pensioner Members [Member]
Pensioner Members [Member]
Charge for the year, net of recoveries
Increase through origination or purchase, financial assets
Statement of changes in equity [table]
Statement of changes in equity [table]
Actuarial assumptions [axis]
Actuarial assumptions [axis]
Joint Radio Company Limited
Joint Radio Company Limited [Member]
Joint Radio Company Limited [Member]
- 20 basis points change in LPI market curve
Market Risk, Limited Price Inflation Market Curve, Twenty Basis Points Decrease [Member]
Market Risk, Limited Price Inflation Market Curve Twenty Basis Points Decrease [Member]
Net cash flow used in investing activities – continuing operations
Cash flows from (used in) investing activities, continuing operations
Other non-cash movements
Increase (Decrease) Through Other Non-Cash Movements, Net Debt
Increase (Decrease) Through Other Non-Cash Movements, Net Debt
Foreign exchange movements
Effect Of Exchange Rate Changes On Net Debt
Effect Of Exchange Rate Changes On Net Debt
Summary Of Dividends [Table]
Summary Of Dividends [Table]
Summary Of Dividends [Table]
Disclosure of classes of share capital [abstract]
Number of shares held in joint operation (in shares)
Number Of Shares Held In Joint Operation
Number Of Shares Held In Joint Operation
Overseas
Foreign Tax Authority [Member]
Foreign Tax Authority [Member]
Cash outflows on derivatives
Cash outflows on derivatives
Cash payments for futures contracts, forward contracts, option contracts and swap contracts, classified as investing activities
Borrowings
Current portion of non-current borrowings
Current borrowings and current portion of non-current borrowings
Number of equity investments valued based on latest transaction price
Number Of Equity Investments Valued Based On Latest Transaction Price
Number Of Equity Investments Valued Based On Latest Transaction Price
Reclassification to held for sale
Increase (Decrease) In Net Debt Through Reclassification To Held For Sale And Discontinued Operations
Increase (Decrease) In Net Debt Through Reclassification To Held For Sale And Discontinued Operations
Derivative effect
Financing And Investing Derivatives [Member]
Financing And Investing Derivatives
Classes of assets [domain]
Classes of assets [domain]
Current Fiscal Year End Date
Current Fiscal Year End Date
Defined contribution plan, employer core contribution as a percent of salary
Defined Contribution Plan, Employer Core Contribution, Percent Of Employees' Gross Pay
Defined Contribution Plan, Employer Core Contribution, Percent Of Employees' Gross Pay
Disposals of property, plant and equipment
Proceeds from sales of property, plant and equipment, classified as investing activities
Pension fund investments in employer issued securities
Pension Fund Investments In Employer Issued Securities, Amount Contributed To Fair Value Of Plan Assets
Pension Fund Investments In Employer Issued Securities, Amount Contributed To Fair Value Of Plan Assets
Types of hedges [domain]
Types of hedges [domain]
Cash dividends paid (in GBP per share)
Dividends paid, ordinary shares per share
Net defined benefit liability (asset) including restrictions on assets recognized
Opening net defined benefit asset
Closing net defined benefit asset including restrictions on the defined benefit assets
Net Defined Benefit Liability (Asset) Including Restrictions On Assets Recognized
Net Defined Benefit Liability (Asset) Including Restrictions On Assets Recognized
Net (losses)/gains on financing derivatives
Gains (Losses) On Derivatives Financial Instruments, Finance Income (Cost)
Gains (Losses) On Derivatives Financial Instruments, Finance Income (Cost)
Fair value gains and losses
Increase (Decrease) Through Changes In Fair Values, Net Debt
Increase (Decrease) Through Changes In Fair Values, Net Debt
Other non-interest-bearing liabilities
Other Non-Derivative Financial Liabilities, Undiscounted Cash Flows
Other Non-Derivative Financial Liabilities, Undiscounted Cash Flows
Proportion of ownership interest in joint venture
Proportion of ownership interest in joint venture
Expense relating to short-term and low-value leases
Expense relating to leases of low-value assets for which recognition exemption has been used
Bottom of range
Bottom of range [member]
Gas Business Enablement system
Gas Business Enablement System [Member]
Gas Business Enablement System
Categories of related parties [axis]
Categories of related parties [axis]
Inflation linked
Inflation-Linked Interest Rate [Member]
Inflation-Linked Interest Rate [Member]
Disclosure of detailed information about borrowings [line items]
Disclosure of detailed information about borrowings [line items]
Defined benefit obligation, member concentration percentage
Defined Benefit Obligation, At Present Value, Member Concentration Percentage
Defined Benefit Obligation, At Present Value, Member Concentration Percentage
+10% market area price change
Market Area Price Risk, Ten Percent Increase [Member]
Market Area Price Risk, Ten Percent Increase
Total profit for the year
Profit for the year
Profit after tax
Profit (loss)
Increase in risk variable, impact on net assets
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Increase In Risk Variable, Impact On Net Assets
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Increase In Risk Variable, Impact On Net Assets
Disclosure of maturity analysis for financial liabilities and derivatives
Disclosure Of Maturity Analysis For Financial Liabilities And Derivatives [Table Text Block]
Disclosure of Maturity Analysis for Financial Liabilities And Derivatives [Table Text Block]
Loss on disposal before tax and reclassification of foreign currency translation reserve
Gain (Loss) On Disposal, Before Tax And Reclassification Of Foreign Currency Translation Reserve
Gain (Loss) On Disposal, Before Tax And Reclassification Of Foreign Currency Translation Reserve
Financial investments
Provision for credit losses of financial assets, beginning balance
Provision for credit losses of financial assets, ending balance
Trade receivables
Assets
Financial assets
Gains on settlement
Gains (losses) arising from settlements, defined benefit plans
Exceptional items and remeasurements
Description of accounting policy for exceptional items [text block]
Total non-current liabilities
Non-current liabilities
Non-current liabilities
Closing foreign exchange rate
Closing foreign exchange rate
5.418% Notes Due 2034
5.418% Notes Due 2034 [Member]
5.418% Notes Due 2034
Less: finance charges allocated to future periods
Lease Liability, Undiscounted Excess Amount
Lease Liability, Undiscounted Excess Amount
Document Registration Statement
Document Registration Statement
Reclassification to held for sale
Increase (Decrease) Through Reclassification To Held For Sale, Liabilities Arising From Financing Activities
Increase (Decrease) Through Reclassification To Held For Sale, Liabilities Arising From Financing Activities
Property
Real estate, amount contributed to fair value of plan assets
Segmental analysis
Disclosure of entity's operating segments [text block]
BritNed Development Limited
BritNed Development Limited [Member]
BritNed Development Limited [Member]
Dividends received from joint ventures, associates and other investments
Dividends Received From Joint Ventures, Associates And Other Investments, Classified As Investing Activities
Dividends Received From Joint Ventures, Associates And Other Investments, Classified As Investing Activities
Depreciation charge for the year
Depreciation, right-of-use assets
Maximum number of treasury shares held during the year (in shares)
Maximum Number Of Treasury Shares Held During The Year
Maximum Number Of Treasury Shares Held During The Year
Temporary difference, unused tax losses and unused tax credits [domain]
Temporary difference, unused tax losses and unused tax credits [domain]
Total for all associates
Total for all associates [member]
Capital commitments
Capital commitments
Accumulated amortisation
Accumulated depreciation
Accumulated depreciation and amortisation [member]
Retained earnings
Retained earnings [member]
Assumed life expectations for a retiree age 65 today: In 20 years: Females
Actuarial Assumption Of Life Expectancy After Retirement In 20 Years, Female
Actuarial Assumption Of Life Expectancy After Retirement In 20 Years, Female
Finance income and costs
Disclosure of finance income (cost) [text block]
Facilities available as backup to specific US borrowings
Facilities Available As Backup To Specific US Borrowings [Member]
Facilities Available As Backup To Specific US Borrowings [Member]
Non-US Subsidiaries
Non-US Subsidiaries [Member]
Non-US Subsidiaries
In 1 to 2 years
Later than one year and not later than two years [member]
Liquefied natural gas
Liquefied Natural Gas [Member]
Liquefied Natural Gas
Disclosure of contingent liabilities [table]
Disclosure of contingent liabilities [table]
Present value of defined benefit obligation
Present value of defined benefit obligation [member]
Change in the real discount rate
Change In Real Discount Rate [Member]
Change In Real Discount Rate
Assets and liabilities not classified as held for sale [member]
Assets and liabilities not classified as held for sale [member]
NGET/SPT Upgrades Limited
NGET/SPT Upgrades Limited [Member]
NGET/SPT Upgrades Limited [Member]
Analysis of income and expense [abstract]
Analysis of income and expense [abstract]
Depreciation and amortisation
Depreciation and amortisation expense
Business Contact
Business Contact [Member]
GBP
United Kingdom, Pounds
Liabilities from financing activities
Liabilities From Financing Activities [Roll Forward]
Liabilities From Financing Activities
Financing derivatives used to hedge debt
Financing Derivatives, Hedging [Member]
Financing Derivatives, Hedging
Benefits paid
Decrease (increase) in net defined benefit liability (asset) resulting from payments from plan
Single ‘A’ range institutions (A)
A Institutions [Member]
A Institutions [Member]
Borrowings
Borrowings1 [Member]
Borrowings1 [Member]
Bonds issued
Bonds issued
Financial assets at amortised cost
Current financial assets at amortised cost
Revenue from performance obligations satisfied or partially satisfied in previous periods
Revenue from performance obligations satisfied or partially satisfied in previous periods
Carrying amount [member]
Carrying amount [member]
Dividends
Disclosure of dividends [text block]
Increase in actuarial assumption, years
Percentage Of Reasonably Possible Change In Actuarial Assumption, Years
Percentage Of Reasonably Possible Change In Actuarial Assumption, Years
Finance Income And Costs [Line Items]
Finance Income And Costs [Line Items]
[Line Items] for Finance Income And Costs [Table]
Derivative financial assets
Current derivative financial assets
Net cash flow (used in)/from financing activities – continuing operations
Cash flows from (used in) financing activities, continuing operations
Hedged borrowings
Hedged item, liabilities
Disclosure Of Detailed Information About Assets Held For Sale [Table]
Disclosure Of Detailed Information About Assets Held For Sale [Table]
Disclosure Of Detailed Information About Assets Held For Sale [Table]
Short-term employee benefits
Key management personnel compensation, short-term employee benefits
Security Exchange Name
Security Exchange Name
Current service cost
Current service cost, defined benefit plans
Net defined benefit asset
Opening net defined benefit asset
Closing net defined benefit asset
Net defined benefit liability (asset)
Disclosure Of Exceptional Items [Table]
Disclosure Of Exceptional Items [Table]
Disclosure Of Exceptional Items
Net increase (decrease) in cash and cash equivalents
Increase (Decrease) In Cash And Cash Equivalents Before Effect Of Exchange Rate Changes, Excluding Bank Overdraft
Increase (Decrease) In Cash And Cash Equivalents Before Effect Of Exchange Rate Changes, Excluding Bank Overdraft
Gains (losses) on disposals of assets held for sale
Gains (Losses) On Disposals Of Assets Held For Sale
Gains (Losses) On Disposals Of Assets Held For Sale
Number of operating business units
Number Of Operating Business Units
Number Of Operating Business Units
Repurchase agreements
Structured Debt, Repurchase Agreements, Amount Contributed To Fair Value Of Plan Assets
Structured Debt, Repurchase Agreements, Amount Contributed To Fair Value Of Plan Assets
Proceeds from issue of treasury shares
Proceeds from sale or issue of treasury shares
Interest received from joint ventures
Interest Received, Related Party Transactions
Interest Received, Related Party Transactions
Treasury stock (in shares)
Treasury Stock, Number Of Shares
Treasury Stock, Number Of Shares
Dividends [Domain]
Dividends Distribution [Domain]
Dividends Distribution
Maximum limit, utilisation
Maximum Exposure To Credit Risk, Utilisation
Maximum Exposure To Credit Risk, Utilisation
Funding surplus/(deficit)
Surplus (deficit) in plan
Cash collateral received/ pledged
Cash collateral pledged subject to enforceable master netting arrangement or similar agreement not set off against financial liabilities
Pensions and other post-retirement benefit obligations
Non-current provisions for employee benefits
Bank loans
Current loans received and current portion of non-current loans received
Right-of-use assets, beginning balance
Right-of-use assets, ending balance
Right-of-use assets
Actuarial assumption of expected rates of salary increases
Actuarial assumption of expected rates of salary increases [member]
Contact Personnel Name
Contact Personnel Name
Eastern Green Link 2 Limited
Eastern Green Link 2 Limited [Member]
Eastern Green Link 2 Limited
Financial assets at amortised cost
Non-current financial assets at amortised cost
Adjustment in respect of post-tax profits of joint ventures and associates included within profit before tax
Tax Effect Of Share Of Profit (Loss) Of Associates And Joint Ventures Accounted For Using Equity Method
Tax Effect Of Share Of Profit (Loss) Of Associates And Joint Ventures Accounted For Using Equity Method
Hedging instrument, liabilities
Hedging instrument, liabilities
Number of shares held in joint venture (in shares)
Number Of Shares Held In Joint Venture
Number Of Shares Held In Joint Venture
Cost efficiency programme, period
Cost Efficiency Programme, Period
Cost Efficiency Programme, Period
Schedule of environmental provision
Environmental Provision [Table Text Block]
Environmental Provision [Table Text Block]
Short-term deposits
Short-term deposits, classified as cash equivalents
Disposals
Disposals, Investments Accounted For Using Equity Method
Disposals, Investments Accounted For Using Equity Method
Net assets
Assets (liabilities)
Assets (liabilities)
Unquoted
Level 2 and 3 of fair value hierarchy [member]
Intangible assets other than goodwill [member]
Intangible assets other than goodwill [member]
Disclosure of fair value of plan assets [table]
Disclosure of fair value of plan assets [table]
US other post retirement benefit costs
Post-Employment Benefit Expense, Defined Benefit Plans, Other Post-retirement Plans
Post-Employment Benefit Expense, Defined Benefit Plans, Other Post-retirement Plans
B Ordinary shares
B Ordinary Shares [Member]
B Ordinary Shares
Schedule of geographical analysis of non-current assets
Schedule of receivables by geographical area
Disclosure of geographical areas [text block]
Items from continuing operations that may be reclassified subsequently to profit or loss:
Items from discontinued operations that may be reclassified subsequently to profit or loss:
Components of other comprehensive income that will be reclassified to profit or loss, net of tax [abstract]
Contract liabilities
Total contract liabilities
As at 1 April
At 31 March
Contract liabilities
Value of buy-in policies offset to actuarial assumption of expected rates of inflation
Value Of Buy-In Policies Offset To Actuarial Assumption Of Expected Rates Of Inflation [Member]
Value Of Buy-In Policies Offset To Actuarial Assumption Of Expected Rates Of Inflation [Member]
Statistical Measurement [Domain]
Statistical Measurement [Domain]
LI Solar Generation, LLC
LI Solar Generation, LLC [Member]
LI Solar Generation, LLC [Member]
Post-employment benefit expense, payroll cost, defined benefit plans
Post-Employment Benefit Expense In Profit Or Loss, Payroll Cost, Defined Benefit Plans
Post-Employment Benefit Expense In Profit Or Loss, Payroll Cost, Defined Benefit Plans
Decommissioning
Provision for decommissioning, restoration and rehabilitation costs [member]
Schedule of reconciliation of changes in allowance account for credit losses
Reconciliation Of Changes In Allowance Account For Credit Losses Of Financial Assets [Table Text Block]
Reconciliation Of Changes In Allowance Account For Credit Losses Of Financial Assets [Table Text Block]
Disposals
Disposals, right-of-use assets
Net operating losses
Unused tax losses [member]
Translation
Reserve of exchange differences on translation [member]
Current service cost
Increase in net defined benefit liability (asset) resulting from current service cost
Liabilities arising from financing activities [axis]
Liabilities arising from financing activities [axis]
Disclosure of amounts recognised in the income statement and statement of other comprehensive income
Disclosure Of Defined Benefit Plan Expense Recognized In Profit Or Loss And Other Comprehensive Income Explanatory [Table Text Block]
Disclosure Of Defined Benefit Plan Expense Recognized In Profit Or Loss And Other Comprehensive Income Explanatory [Table Text Block]
Debt covenants, total debt, headroom
Debt Covenants, Total Debt, Headroom
Debt Covenants, Total Debt, Headroom
Financial and other investments
Other non-current financial assets
Other non-current financial assets
Amortised period (in years)
Useful life measured as period of time, intangible assets other than goodwill
Decommissioning provision, ARO
Provision For Decommissioning, ARO [Member]
Provision for decommissioning, ARO [Member]
Tax on share-based payments
Decrease (increase) through tax on share-based payment transactions, equity
Classes of share capital [axis]
Classes of share capital [axis]
Disclosure of fair value measurement of liabilities [table]
Disclosure of fair value measurement of liabilities [table]
Variable lease payments included in lease income
Expense relating to variable lease payments not included in measurement of lease liabilities
Reclassification to held for sale
Decrease through classified as held for sale, goodwill
Basis of consolidation
Disclosure of basis of consolidation [text block]
Expenses not deductible for tax purposes
Tax effect of expense not deductible in determining taxable profit (tax loss)
Extension of term of borrowing facilities
Extension Of Term Of Borrowing Facilities [Member]
Extension Of Term Of Borrowing Facilities
Included within finance income and costs
Included Within Finance And Costs [Abstract]
Included Within Finance And Costs
Equity, beginning balance
Equity, ending balance
Total equity
Equity
Non-current
Non-Current Derivative [Member]
Non-Current Derivative Financial Assets [Member]
Entity Addresses, Address Type [Axis]
Entity Addresses, Address Type [Axis]
Financial assets (liabilities)
Financial assets (liabilities) at beginning of period
Financial assets (liabilities) at end of period
Financial Assets (Liabilities)
Financial Assets (Liabilities)
Disclosure of detailed information about derivative financial instruments
Disclosure Of Detailed Information About Derivative Financial Instruments Explanatory [Table Text Block]
Disclosure Of Detailed Information About Derivative Financial Instruments Explanatory [Table Text Block]
Gas swaps
Commodity Derivatives - Gas Swaps [Member]
Commodity Derivatives - Gas Swaps [Member]
Gross amounts offset
Gross Financial Liabilities (Assets) Set Off Against Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements
Gross Financial Liabilities (Assets) Set Off Against Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements
Other assurance services
Auditor's Remuneration For Other Services, Other Assurance Services
Auditor's Remuneration For Other Services, Other Assurance Services
Subsidiaries of an associate
Subsidiaries Of An Associate [Member]
Subsidiaries Of An Associate
Derivative financial liabilities
Derivative financial liabilities, undiscounted cash flows
Specific project
Investments, Specific Project [Member]
Investments, Specific Project
Weighted average duration of defined benefit obligation
Weighted average duration of defined benefit obligation
US Regulated
US Regulated [Member]
US Regulated [Member]
Other assets
Other assets
Items from continuing operations that will never be reclassified to profit or loss:
Components of other comprehensive income that will not be reclassified to profit or loss, net of tax [abstract]
Value of security arrangements
Defined Benefit Plan, Deficit, Security Arrangement, Value
Defined Benefit Plan, Deficit, Security Arrangement, Value
Level 1
Quoted
Level 1 of fair value hierarchy [member]
Finance income
Finance Income [Abstract]
Finance Income
Current
Current borrowings and current portion of non-current borrowings, by type [abstract]
Gain/(loss) on disposal
Post-tax loss on disposal
Gain (Loss) Recognised On Measurement To Fair Value Less Costs To Sell Or On Disposal Of Assets Or Disposal Groups Constituting Discontinued Operation, After Tax
Gain (Loss) Recognised On Measurement To Fair Value Less Costs To Sell Or On Disposal Of Assets Or Disposal Groups Constituting Discontinued Operation, After Tax
Retirement Plans, Name [Domain]
Retirement Plans, Name [Domain]
Retirement Plans, Name [Domain]
Disclosure of detailed information about property, plant and equipment [line items]
Disclosure of detailed information about property, plant and equipment [line items]
Change in estimated future cash flows
Change In Estimated Future Cash Flows Change [Member]
Change In Estimated Future Cash Flows Change [Member]
Undrawn borrowing facilities
Undrawn borrowing facilities
Capitalisation rate of borrowing costs eligible for capitalisation
Capitalisation rate of borrowing costs eligible for capitalisation
Current assets
Current Assets [Member]
Current Assets [Member]
UELs limited to 2070, impact on depreciation expense
Sensitivity Analysis, Useful Economic Life Limited To 2070, Impact On Depreciation Expense
Sensitivity Analysis, Useful Economic Life Limited To 2070, Impact On Depreciation Expense
Level 2
Level 2 of fair value hierarchy [member]
IFA fire
Income from reimbursements under insurance policies
Disclosure of non-adjusting events after reporting period [abstract]
Disclosure of non-adjusting events after reporting period [abstract]
US Subsidiaries
US Subsidiaries [Member]
US Subsidiaries
Dividends paid to shareholders
Dividends paid, classified as financing activities
–20 basis points change in LPI market curve
Sensitivity Analysis, 20 Basis Point Change Decrease In Market Curve
Sensitivity Analysis, 20 Basis Point Change Decrease In Market Curve
Equity shareholders of the parent
Profit (loss), attributable to owners of parent
Net Debt [Line Items]
Net Debt [Line Items]
[Line Items] for Net Debt [Table]
Change in value used for calculating ineffectiveness, Hedged item
Gain (loss) on change in fair value of hedged item used as basis for recognising hedge ineffectiveness
Other equity reserves
Description Of Accounting Policy For Other Equity Reserves [Policy Text Block]
Description of Accounting Policy for Other Equity Reserves [Policy Text Block]
Other environment related provision
Environmental
Other environment related provision [member]
Other non-current assets
Other Non-Current Assets [Member]
Other Non-Current Assets
Changes in provisions
Adjustments for provisions
Net debt
Disclosure Of Net Debt [Text Block]
Disclosure Of Net Debt [Text Block]
Reclassifications to other payables (note 24)
Increase (decrease) through transfers and other changes, other provisions
Increase (decrease) through transfers and other changes, other provisions
30 – 60 days past due
Later than one month and not later than two months [member]
Other non-current assets
Description of accounting policy for non-current assets or disposal groups classified as held for sale [text block]
Reclassifications
Increase (decrease) through transfers, property, plant and equipment including right-of-use assets
Exchange adjustments
Other Comprehensive Income, Before Tax, Exchange Differences On Exchange Translation And Hedges Of Net Investments In Foreign Operations
Other Comprehensive Income, Before Tax, Exchange Differences On Exchange Translation And Hedges Of Net Investments In Foreign Operations
Interest on derivatives
Interest Expense On Derivatives
Interest Expense On Derivatives
Interest (charges)/income
Increase (Decrease) Through Interest Income (Expenses), Financial Investments
Increase (Decrease) Through Interest Income (Expenses), Financial Investments
Employer contributions, excluding recovery plan payments
Defined Benefit Plan, Employer Contributions, Excluding Recovery Plan Payments
Defined Benefit Plan, Employer Contributions, Excluding Recovery Plan Payments
Deferred tax liability (asset) beginning of period
Deferred tax liability (asset) end of period
Deferred tax liability
Deferred tax liability (asset)
Total current liabilities
Current liabilities
Current liabilities
New England
New England Segment [Member]
New England Segment
Cash flow hedges
Cash flow hedges [member]
East Midlands
East Midlands [Member]
East Midlands
Deferred tax:
Deferred Income Tax Relating To Components Of Other Comprehensive Income And Items Credited (Charged) Directly To Equity [Abstract]
Deferred Income Tax Relating To Components Of Other Comprehensive Income And Items Credited (Charged) Directly To Equity [Abstract]
Trade and other receivables [abstract]
Trade and other receivables [abstract]
Debt covenants, borrowings excluding cash and short term investments, headroom
Debt Covenants, Borrowings Excluding Cash And Short Term Investments, Headroom
Debt Covenants, Borrowings Excluding Cash And Short Term Investments, Headroom
Continuing and discontinued operations [axis]
Continuing and discontinued operations [axis]
Deferred tax assets
Deferred tax assets
Inventories
Inventories and current intangible assets
Current inventories
Non-controlling interests
Non-controlling interests [member]
Non-controlling interests
Comprehensive income, attributable to non-controlling interests
Document Accounting Standard
Document Accounting Standard
Social security and other taxes
Current payables on social security and taxes other than income tax
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Disclosure of quantitative information about right-of-use assets [line items]
Disclosure of quantitative information about right-of-use assets [line items]
Other operating costs
Disclosure of other operating expense [text block]
Number of Superfund sites
Number Of Superfund Sites
Number Of Superfund Sites
Disclosure of joint ventures [table]
Disclosure of joint ventures [table]
Assumed life expectations for a retiree age 65 today: Males
Actuarial Assumption Of Life Expectancy After Retirement, Male
Actuarial Assumption Of Life Expectancy After Retirement, Male
Total (loss)/gain included in the statement of other comprehensive income
Other Comprehensive Income, Net Of Tax, Gains (Losses) On Remeasurement And Foreign Exchange Rates, Net Defined Benefit Plan
Other Comprehensive Income, Net Of Tax, Gains (Losses) On Remeasurement And Foreign Exchange Rates, Net Defined Benefit Plan
Statement of changes in equity [abstract]
Statement of changes in equity [abstract]
Retained earnings
Retained earnings
Measurement [domain]
Measurement [domain]
Gross carrying amounts
Gross financial assets subject to offsetting, enforceable master netting arrangements or similar agreements
Other comprehensive loss
Other Comprehensive Income/(Loss) For The Year, Net Of Tax, From Continuing Operations
Other Comprehensive Income/(Loss) For The Year, Net Of Tax, From Continuing Operations
Debt instruments
Debt instruments, amount contributed to fair value of plan assets
Final dividend in respect of the prior year
Final Dividend In Respect Of Prior Year [Member]
Final Dividend in Respect of Prior Year [Member]
Actuarial gains/(losses) – financial assumptions
Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions
Net gains/(losses) for the year
Gains (Losses) Recognized In Profit Or Loss, Fair Value Measurement, Assets (Liabilities)
Gains (Losses) Recognized In Profit Or Loss, Fair Value Measurement, Assets (Liabilities)
Maximum limit
Maximum exposure to credit risk
5.602% Notes Due 2028
5.602% Notes Due 2028 [Member]
5.602% Notes Due 2028
Disclosure of detailed information about financial instruments [line items]
Disclosure of detailed information about financial instruments [line items]
Net gains on investment in debt instruments measured at fair value through other comprehensive income
Net (losses)/gains on investments in debt instruments measured at fair value through other comprehensive income
Gains (Losses) On Investments In Debt Instruments Measured At Fair Value Through Other Comprehensive Income
Net gains/(losses) on investments in debt instruments measured at fair value through OCI
Actuarial assumption of expected rates of inflation
Actuarial assumption of expected rates of inflation [member]
Balance Sheet Location [Domain]
Balance Sheet Location1 [Domain]
Balance Sheet Location1
Types of risks [domain]
Types of risks [domain]
System Operator
System Operator [Member]
System Operator[Member]
Gain on sale of investments
Adjustments for gain (loss) on disposal of investments in subsidiaries, joint ventures and associates
Legal Entity [Axis]
Legal Entity [Axis]
Derivative assets
Derivative financial assets
Subsidiaries [axis]
Subsidiaries [axis]
Cash flow projection, forecast period
Cash Flow Projection, Forecast Period
Cash Flow Projection, Forecast Period
Areas of judgement and key sources of estimation uncertainty
Description Of Accounting Policy For Accounting Estimates [Policy Text Block]
Description Of Accounting Policy For Accounting Estimates [Policy Text Block]
Basic total earnings
Profit (loss), attributable to ordinary equity holders of parent entity, used in calculating basic earnings per share
Impact of climate change and the transition to net zero
Description Of Accounting Policy For Impact Of Climate Change And Transition To Net Zero [Policy Text Block]
Description Of Accounting Policy For Impact Of Climate Change And Transition To Net Zero
Going concern
Disclosure of going concern [text block]
Actuarial assumption of discount rates
Actuarial assumption of discount rates [member]
Deferred tax impact of change in UK tax rate
Tax effect from change in tax rate
Disclosure of detailed information about hedged items
Disclosure of detailed information about hedged items [text block]
Energis plc
Energis PLC [Member]
Energis plc [Member]
Segmental analysis
Description of accounting policy for segment reporting [text block]
Actuarial gains/(losses) – demographic assumptions
Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in demographic assumptions
Geographical areas [axis]
Geographical areas [axis]
Net defined benefit liability (asset) [domain]
Net defined benefit liability (asset) [domain]
Derivative non-monetary notional amount
Derivative, Non-Monetary Notional Amount
Derivative, Non-Monetary Notional Amount
Restricted cash and cash equivalents
Restricted cash and cash equivalents
Issued capital beginning balance (in shares)
Issued capital ending balance (in shares)
Number of shares issued and fully paid
Liabilities arising from financing activities at start of year
Liabilities arising from financing activities at end of year
Liabilities arising from financing activities
+100 basis points change in discount rate
Sensitivity Analysis, 50 Basis Point Change Increase In Discount Rate
Sensitivity Analysis, 50 Basis Point Change Increase In Discount Rate
-20 basis points decrease between RPI and CPI
Market Risk, Retail Price Index & Consumer Price Index, Twenty Basis Points Decrease [Member]
Market Risk, Retail Price Index & Consumer Price Index, Twenty Basis Points Decrease
Interest expense on financial liabilities held at amortised cost:
Interest costs [abstract]
Lease liabilities
Non-current lease liabilities
Aggregated individually immaterial associates and joint ventures
Aggregated Individually Immaterial Associates and Joint Ventures [Member]
Aggregated Individually Immaterial Associates and Joint Ventures
All other current assets
Current Assets Excluding Cash And Cash Equivalents
Current Assets Excluding Cash And Cash Equivalents
Balance of fair value hedge adjustments in borrowings, Continuing hedges
Accumulated fair value hedge adjustment on hedged item included in carrying amount, liabilities
Revenue
Disclosure of revenue from contracts with customers [text block]
Entity Common Stock, Shares Outstanding
Entity Common Stock, Shares Outstanding
Number of equity investments valued based on internal valuation process
Number Of Equity Investments Valued Based On Internal Valuation Process
Number Of Equity Investments Valued Based On Internal Valuation Process
Changes in net defined benefit liability (asset) [abstract]
Changes in net defined benefit liability (asset) [abstract]
Schedule of average expected loss rates and balances
Disclosure of provision matrix [text block]
Net debt position
Net debt at start of year
Net debt at end of year
Net debt
Liabilities extinguished on settlements
Decrease (Increase) In Net Defined Benefit Liability (Asset) Resulting From Liabilities Extinguished In Respect Of Settlements
Decrease (Increase) In Net Defined Benefit Liability (Asset) Resulting From Liabilities Extinguished In Respect Of Settlements
Other intangible assets
Intangible assets other than goodwill, beginning balance
Intangible assets other than goodwill, ending balance
Intangible assets other than goodwill
Document Financial Statement Error Correction [Flag]
Document Financial Statement Error Correction [Flag]
New York Transco LLC
New York Transco LLC [Member]
New York Transco LLC [Member]
Derivative financial liabilities
Non-current derivative financial liabilities
Exceptional items
Exceptional Items, Netting [Member]
Exceptional items [Member]
Disposals
Disposals, intangible assets other than goodwill
Segments [domain]
Segments [domain]
Cash and cash equivalents
Cash and cash equivalents
Cash and cash equivalents at start of year
Cash and cash equivalents at end of year
Cash and cash equivalents
Cash flow hedges transferred to the statement of financial position, net of tax
Increase (Decrease) Through Cash Flow Hedges Transferred To The Statement Of Financial Position, After Tax, Equity
Increase (Decrease) Through Cash Flow Hedges Transferred To The Statement Of Financial Position, After Tax, Equity
Other non-current liabilities
Other Non-Current Liabilities [Member]
Other Non-Current Liabilities
Classes of ordinary shares [axis]
Classes of ordinary shares [axis]
Financial liabilities
Financial Liabilities, Undiscounted Cash Flows
Financial Liabilities, Undiscounted Cash Flows
Disposal of financial and other investments
Proceeds from sales of investments other than investments accounted for using equity method
Payroll costs including capitalised costs
Employee Benefits Including Capitalised Costs
Employee Benefits Including Capitalised Costs
Tax
Tax expense (income) relating to profit (loss) from ordinary activities of discontinued operations
Disclosure Of Income Taxes [Table]
Disclosure Of Income Taxes [Table]
Disclosure Of Income Taxes [Table]
Disclosure of non-adjusting events after reporting period [line items]
Disclosure of non-adjusting events after reporting period [line items]
Joint operations [axis]
Joint operations [axis]
Change in risk variable, percent
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Percent
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Percent
Reclassification to held for sale
Increase (Decrease) In Cash And Cash Equivalents Through Reclassification To Held For Sale And Discontinued Operations
Increase (Decrease) In Cash And Cash Equivalents Through Reclassification To Held For Sale And Discontinued Operations
+ 20 basis points change in Limited Price Inflation (LPI) market curve
Market Risk, Limited Price Inflation Market Curve, Twenty Basis Points Increase [Member]
Market Risk, Limited Price Inflation Market Curve Twenty Basis Points Increase [Member]
Balance of fair value hedge adjustments in borrowings, Discontinued hedges
Accumulated fair value hedge adjustment remaining in statement of financial position for hedged item that ceased to be adjusted for hedging gains and losses, liabilities
Cash collateral received/ pledged
Cash collateral received subject to enforceable master netting arrangement or similar agreement not set off against financial assets
Schedule of transactions between related parties
Disclosure of transactions between related parties [text block]
Schedule of borrowings
Disclosure of detailed information about borrowings [text block]
Settlements
Sales, Fair Value Measurement, Assets (Liabilities)
Sales, Fair Value Measurement, Assets (Liabilities)
Lease liabilities
Temporary Differences, Lease Liabilities [Member]
Temporary Differences, Lease Liabilities
US
UNITED STATES
Exchange adjustments
Increase (decrease) through net exchange differences, other provisions
Property, plant and equipment [abstract]
Property, plant and equipment [abstract]
Assets
Net financial assets subject to offsetting, enforceable master netting arrangements or similar agreements [abstract]
Corporate bonds
Corporate Bonds, Netting [Member]
Corporate Bonds, Netting [Member]
Provisions
Provisions
Land and buildings
Freehold and leasehold buildings
Land and buildings [member]
Regulatory licenses
Regulatory Licenses [Member]
Regulatory Licenses
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information1 [Abstract]
Supplemental Cash Flow Information1
Double ‘A+’ G7 sovereign entities (AA+)
AA Plus G7 Sovereign Entities [Member]
AA Plus G7 Sovereign Entities [Member]
Less: payroll costs capitalised
Employee Costs Capitalised
Employee Costs Capitalised
Employer contributions, recovery plan payments
Defined Benefit Plan, Employer Contributions, Recovery Plan, Annual Payments
Defined Benefit Plan, Employer Contributions, Recovery Plan, Annual Payments
Income Tax Authority [Axis]
Income Tax Authorities [Axis]
Income Tax Authorities [Axis]
Other comprehensive (loss)/income for the year from discontinued operations, net of tax
Other Comprehensive Income/(Loss) For The Year, Net Of Tax, From Discontinued Operations
Other Comprehensive Income/(Loss) For The Year, Net Of Tax, From Discontinued Operations
Administration costs
Administration costs not reflected in return on plan assets, defined benefit plans
Liabilities – non-current
Long-term borrowings [member]
Inventory consumed
Raw materials and consumables used
Future revenues in relation to unfulfilled performance obligations
Transaction price allocated to remaining performance obligations
Provision for impairment of receivables and accrued income
Provision For Impairment Of Receivables And Accrued Income
Provision For Impairment Of Receivables And Accrued Income
Joint ventures [domain]
Joint ventures [domain]
Investments in joint ventures and associates
Description of accounting policy for investment in associates and joint ventures [text block]
Joint operations [domain]
Joint operations [domain]
Other
Other Net Assets (Liabilities) Amount Contributed To Fair Value Of Plan Assets
Other Net Assets (Liabilities) Amount Contributed To Fair Value Of Plan Assets
Schedule of lease obligations
Disclosure of maturity analysis for non-derivative financial liabilities [text block]
Electricity generation plant
Electricity Generation Plant [Member]
Electricity Generation Plant [Member]
Electralink Limited
Electralink Limited [Member]
Electralink Limited
Foreign exchange movements
Increase (decrease) through effect of changes in foreign exchange rates, liabilities arising from financing activities
Net losses on financial instruments
Net Losses On Financial Instruments, Included Within Share Of Post-Tax Results Of Joint Ventures And Associates
Net Losses On Financial Instruments, Included Within Share Of Post-Tax Results Of Joint Ventures And Associates
Disclosure of detailed information about hedging instruments
Disclosure of detailed information about hedging instruments [text block]
Debt covenants, total debt
Debt Covenants, Total Debt
Debt Covenants, Total Debt
Interest rate risk
Interest rate risk [member]
City Area Code
City Area Code
Purchases of electricity
Cost Of Purchased Electricity
Cost Of Purchased Electricity
Exchange adjustments
Increase (Decrease) Relating To Exchange Adjustments, Contract Liabilities
Increase (Decrease) Relating To Exchange Adjustments, Contract Liabilities
South Wales
South Wales [Member]
South Wales
Commitments and contingencies
Description of accounting policy for contingent liabilities and contingent assets [text block]
Contract liabilities
Disclosure Of Contract Liabilities [Text Block]
Disclosure of Contract Liabilities [Text Block]
Debt covenants, borrowings excluding cash and short term investments
Debt Covenants, Borrowings Excluding Cash And Short-Term Investments
Debt Covenants, Borrowings Excluding Cash And Short-Term Investments
Defined contribution plan, employer matching contribution, percent of match
Defined Contribution Plan, Employer Matching Contribution, Percent Of Match Contributions
Defined Contribution Plan, Employer Matching Contribution, Percent Of Match Contributions
New York
New York CGU [Member]
New York CGU [Member]
USD
United States of America, Dollars
Disclosure of net defined benefit liability (asset) [table]
Disclosure of net defined benefit liability (asset) [table]
Diluted EPS
Diluted earnings per share [abstract]
Total other services
Auditor's Remuneration For Tax And Other Services
Auditor's Remuneration For Tax And Other Services
National Grid UK Retirement Plan (NGUKRP)
National Grid UK Retirement Plan [Member]
National Grid UK Retirement Plan
Summary of contract liabilities
Summary Of Contract Liabilities [Table Text Block]
Summary of Contract Liabilities [Table Text Block]
Asset useful life
Useful economic life, property, plant and equipment
Useful life measured as period of time, property, plant and equipment
More than 5 years
Later than five years [member]
Interest paid to joint ventures
Interest Paid Related, Party Transaction
Interest Paid Related, Party Transaction
Total comprehensive income for the year from discontinued operations
Comprehensive income from discontinued operations
Fair value gains and losses
Increase (Decrease) Through Changes In Fair Values, Other Financing Derivatives
Increase (Decrease) Through Changes In Fair Values, Other Financing Derivatives
One-off contribution to net defined benefit liability (asset)
Net Defined Benefit Liability (Asset), One-Off Employer Contribution
One-Off Contribution Net Defined Benefit Liability (Asset)
Related party transactions
Disclosure of related party [text block]
Classes of financial assets [domain]
Classes of financial assets [domain]
Other intangible assets
Disclosure of intangible assets [text block]
Non-current intangible assets
Non-Current Intangible Assets [Member]
Non-Current Intangible Assets
Transferred to profit or loss
Reclassification Of Items Transferred To Profit (Loss)
Reclassification Of Items Transferred To Profit (Loss)
Level 3
Level 3 of fair value hierarchy [member]
Disclosure of reconciliation of changes in intangible assets and goodwill [table]
Disclosure of reconciliation of changes in intangible assets and goodwill [table]
Disposals
Disposals, property, plant and equipment including right-of-use assets
Total tax recognised in the statements of comprehensive income from continuing operations
Income tax relating to components of other comprehensive income
UK Electricity Transmission
UK Electricity Transmission [Member]
UK Electricity Transmission [Member]
Interest expense on lease liabilities
Interest expense on lease liabilities
Total
Derivative Financial Assets (Liabilities)
Derivative Financial Assets (Liabilities)
Disposal-related costs
Disposal Related Costs on Disposal of Assets
Disposal Related Costs on Disposal of Assets
Other operating costs
Description of accounting policy for expenses [text block]
Disclosure of classes of share capital [table]
Disclosure of classes of share capital [table]
Auditor Name
Auditor Name
Investment in joint venture
Investments in joint ventures reported in separate financial statements
Uncollectible amounts written off
Decrease through write-off, financial assets
Segment consolidation items [domain]
Segment consolidation items [domain]
Disclosure of disaggregation of revenue from contracts with customers [line items]
Disclosure of disaggregation of revenue from contracts with customers [line items]
Liabilities
Net financial liabilities subject to offsetting, enforceable master netting arrangements or similar agreements [abstract]
West Midlands
West Midlands [Member]
West Midlands
Emerald Energy Venture LLC
Emerald Energy Venture LLC [Member]
Emerald Energy Venture LLC [Member]
Interconnector plant and other
Interconnector Plant And Other [Member]
Interconnector Plant [Member]
Trade and other receivables
Disclosure of trade and other receivables [text block]
Financial and other investments
Other current financial assets
Current financial investments
Financial investments at start of year
Financial investments at end of year
Other current financial assets
+10% market area price change
Sensitivity Analysis, 10 Percent Increase In Market Area Price Change
Sensitivity Analysis, 10 Percent Increase In Market Area Price Change
Other
Other Financial Instruments [Member]
Other Financial Instruments [Member]
Summary Of Dividends [Line Items]
Summary Of Dividends [Line Items]
[Line Items] for Summary Of Dividends [Table]
Past due status [axis]
Past due status [axis]
Goodwill
Goodwill [member]
Investments in joint ventures and associates
Subsidiary undertakings, joint ventures and associates
Disclosure of interests in other entities [text block]
Non-current liabilities
Non-current liabilities [abstract]
Assets held for sale and discontinued operations
Disclosure of non-current assets held for sale and discontinued operations [text block]
Entity [Domain]
Entity [Domain]
Past service cost – redundancies
Past Service Cost, Augmentations And Redundancies, Defined Benefit Plans
Past Service Cost, Augmentations And Redundancies, Defined Benefit Plans
Other operating income
Miscellaneous other operating income
Motor vehicles and office equipment
Motor Vehicles And Office Equipment [Member]
Motor Vehicles And Office Equipment [Member]
Pensions and other post- retirement benefits
Pensions And Other Post-Retirement Benefits, Related Temporary Differences [Member]
Pensions And Other Post-retirement Benefits Related Temporary Differences [Member]
Electricity options
Commodity Derivatives - Electricity Options [Member]
Commodity Derivatives - Electricity Options [Member]
Capital investment
Additions To Property, Plant And Equipment, Non-Current Intangible Assets And Equity Method Investments
Additions To Property, Plant And Equipment, Non-Current Intangible Assets And Equity Method Investments
Document Fiscal Year Focus
Document Fiscal Year Focus
10% increase in commodity prices
Sensitivity Analysis, 10 Percent Increase In Commodity Prices
Sensitivity Analysis, 10 Percent Increase In Commodity Prices
Adjustments for:
Adjustments to reconcile profit (loss) [abstract]
Transferred to profit or loss in respect of cost of hedging
Reclassification Adjustments On Change In Value Of Forward Elements Of Forward Contracts And Foreign Currency Basis Spreads, Before Tax
Reclassification Adjustments On Change In Value Of Forward Elements Of Forward Contracts And Foreign Currency Basis Spreads, Before Tax
Actual return on plan assets
Return On Plan Assets, Including Interest Income, Net Defined Benefit Liability (Asset)
Return On Plan Assets, Including Interest Income, Net Defined Benefit Liability (Asset)
Over 12 months past due
Long-term limit
Later than one year [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Total operating costs from continuing operations
Operating Expenses From Continuing Operations
Operating Expenses From Continuing Operations
+20 basis points increase between RPI and Consumer Price Index (CPI)
Market Risk, Retail Price Index & Consumer Price Index, Twenty Basis Points Increase [Member]
Market Risk, Retail Price Index & Consumer Price Index, Twenty Basis Points Increase
Reclassification adjustments on retranslation of operations, before tax
Reclassification Adjustments On Retranslation of Operations, Before Tax
Reclassification Adjustments On Retranslation of Operations, Before Tax
Financial instruments
Financial Instruments Related Temporary Differences [Member]
Financial Instruments Related Temporary Differences [Member]
Schedule of undrawn committed borrowing facilities
Disclosure Of Undrawn Borrowing Facilities [Table Text Block]
Disclosure Of Undrawn Borrowing Facilities [Table Text Block]
KHB Venture LLC
KHB Venture LLC [Member]
KHB Venture LLC [Member]
Investments in forestry funds
Forestry Funds Investments
Forestry Funds Investments
Major Transformation Programme
Major Transformation Programme [Member]
Major Transformation Programme
Types of interest rates [domain]
Types of interest rates [domain]
Connections
Connections [Member]
Connections [Member]
Other income
Other income
Classes of other provisions [axis]
Classes of other provisions [axis]
Purchases of gas
Cost Of Purchased Gas
Cost Of Purchased Gas
Reclassification/transfer out of level 3
Increase (Decrease) Through Reclassification Of Level 3, Fair Value Measurement, Assets (Liabilities)
Increase (Decrease) Through Reclassification Of Level 3, Fair Value Measurement, Assets (Liabilities)
New IFRS accounting standards and interpretations not yet adopted
Disclosure of expected impact of initial application of new standards or interpretations [text block]
Aviva
Aviva [Member]
Aviva
Net gains/(losses) in respect of cash flow hedging of capital expenditure
Other Comprehensive Income, Before Tax, Gains (Losses) In Respect Of Cash Flow Hedging Of Capital Expenditure
Other Comprehensive Income, Before Tax, Gains (Losses) In Respect Of Cash Flow Hedging Of Capital Expenditure
Current tax:
Current tax expense (income) and adjustments for current tax of prior periods [abstract]
Diluted earnings from discontinued operations
Profit (loss) from discontinued operations attributable to ordinary equity holders of parent entity, used in calculating diluted earnings per share
LI Energy Storage System, LLC
LI Energy Storage System, LLC [Member]
LI Energy Storage System, LLC [Member]
Trade payables
Current trade payables
Schedule of impacts of reasonably possible changes in significant level 3 assumptions
Sensitivity analysis for types of market risk [text block]
Other
Other Currency [Member]
Total key management compensation
Key management personnel compensation
Pension plan
Pension Defined Benefit Plans, Related Party [Member]
Pension Defined Benefit Plans, Related Party
Included within tax
Included Within Tax [Abstract]
Included Within Tax
Derivative liabilities
Derivative financial liabilities
Schedule of cash and cash equivalents
Disclosure Of Cash And Cash Equivalents Explanatory [Table Text Block]
Disclosure Of Cash And Cash Equivalents Explanatory [Table Text Block]
US And Non-US subsidiaries
US And Non-US subsidiaries [Member]
US And Non-US subsidiaries
Disclosure of credit risk exposure [line items]
Disclosure of credit risk exposure [line items]
Characteristics of defined benefit plans [axis]
Characteristics of defined benefit plans [axis]
Disclosure of actuarial assumptions
Disclosure of defined benefit plans [text block]
Disclosure of maturity analysis for non-derivative financial liabilities [table]
Disclosure of maturity analysis for non-derivative financial liabilities [table]
3 – 6 months past due
Later than three months and not later than six months [member]
Ordinary shares
Ordinary shares [member]
Trade receivables
Current trade receivables
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Table]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Table]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Table]
Effect of dilutive potential ordinary shares – employee share plans (in shares)
Dilutive effect of share options on weighted average number of ordinary shares
Allowance for credit losses
Allowance for credit losses [member]
Schedule of allocation of goodwill by operations
Disclosure Of Detailed Information About Intangible Assets And Goodwill Allocated By Operation [Table Text Block]
Disclosure Of Detailed Information About Intangible Assets And Goodwill Allocated By Operation
Impairment of joint venture
Impairment of joint venture
Impairment Of Associates And Joint Ventures Accounted For Using Equity Method
Impairment Of Associates And Joint Ventures Accounted For Using Equity Method
Liabilities held for sale
Liabilities included in disposal groups classified as held for sale
Cost efficiency programme, annual savings, target
Cost Efficiency Programme, Annual Savings, Target
Cost Efficiency Programme, Annual Savings, Target
Change in actuarial assumption, percent
Percentage Of Reasonably Possible Change In Actuarial Assumption, Percent
Percentage Of Reasonably Possible Change In Actuarial Assumption, Percent
Commodity contract derivatives
Commodity Derivatives [Member]
Commodity Derivatives [Member]
Earnings per share (EPS)
Disclosure of earnings per share [text block]
Investments in short-term money market funds
Investments, Short-Term Money Market Funds [Member]
Investments, Short-Term Money Funds [Member]
Gross carrying amount
Cost
Gross carrying amount [member]
Trade and other payables
Trade and other payables
Trade and other current payables
Net proceeds from issue of ordinary shares
Net Proceeds From Issue Of Ordinary Shares
Net Proceeds From Issue Of Ordinary Shares
Past service cost – augmentations and redundancies
Increase (Decrease) In Net Defined Benefit Liability (Asset) Resulting From Past Service Cost, Augmentations And Redundancies
Increase (Decrease) In Net Defined Benefit Liability (Asset) Resulting From Past Service Cost, Augmentations And Redundancies
Inventories
Disclosure of inventories [text block]
Local Phone Number
Local Phone Number
Proceeds from issuing shares
Proceeds from issuing shares
Less than 1 year
Not later than one year [member]
Borrowings, term
Borrowings, Term
Borrowings, Term
Income Tax Authority [Domain]
Income Tax Authorities [Domain]
Income Tax Authorities
Net gains (losses) in respect of net investment hedges
Gains (losses) on hedges of net investments in foreign operations, before tax
Non-current
Non-current portion of non-current borrowings, by type [abstract]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
[Line Items] for Disclosure Of Fair Value Measurement Of Assets And Liabilities [Table]
Liability for interconnector excess revenues
Liability For Interconnector Excess Revenues [Member]
Liability For Interconnector Excess Revenues
Return-seeking assets
Return-Seeking Assets, Amount Contributed To Fair Value Of Plan Assets, Percentage
Return-Seeking Assets, Amount Contributed To Fair Value Of Plan Assets, Percentage
Joint ventures and associates
Joint Ventures And Associates [Member]
Joint Ventures And Associates
Total auditor’s remuneration
Auditor's remuneration
Schedule of remeasurement, tax exceptional items and tax effect of exceptional items
Schedule Of Remeasurement, Tax Exceptional Items and Tax Effect Of Exceptional Items [Table Text Block]
Schedule Of Remeasurement, Tax Exceptional Items and Tax Effect Of Exceptional Items
Gearing ratio
Gearing Ratio
Gearing Ratio
Borrowings
Non-current portion of non-current borrowings
Non-current portion of non-current borrowings
Net amount presented in statement of financial position
Net financial assets subject to offsetting, enforceable master netting arrangements or similar agreements in statement of financial position
Disclosure of financial assets [line items]
Disclosure of financial assets [line items]
Property, plant and equipment
Property, plant and equipment [member]
Property, plant and equipment
Description of accounting policy for property, plant and equipment [text block]
Proceeds received from loans
Proceeds received from loans
Proceeds from borrowings, classified as financing activities
Payments of lease liabilities
Payments of lease liabilities
Payments of lease liabilities, classified as financing activities
Foreign currency and interest rate risk
Market risk [member]
Entity Voluntary Filers
Entity Voluntary Filers
Other non-current liabilities
Description Of Accounting Policy For Other Non-current Liabilities [Policy Text Block]
Description Of Accounting Policy For Other Non-current Liabilities [Policy Text Block]
Fair value gains and losses
Increase (decrease) through changes in fair values, liabilities arising from financing activities
Disclosure of most significant risks associated with DB plans
Disclosure of additional information about defined benefit plans [text block]
Proportion of ownership interest in subsidiary
Proportion of ownership interest in subsidiary
Balance in translation reserve, Continuing hedges
Reserve of exchange differences on translation, continuing hedges
Entity Registrant Name
Entity Registrant Name
Basic earnings per share (continuing and discontinued) (in GBP pence per share)
Total basic earnings per share (in GBP per share)
Basic earnings (loss) per share
Gross proceeds from reissue of treasury shares
Proceeds From Sale Or Issue Of Treasury Shares, Gross
Proceeds From Sale Or Issue Of Treasury Shares, Gross
Liquidity risk
Liquidity risk [member]
Restrictions on the defined benefit asset
Restrictions On Defined Benefit Assets Recognized
Restrictions On Defined Benefit Assets Recognized
Measurement [axis]
Measurement [axis]
Weighted average number of shares – diluted (in shares)
Weighted average number of shares – diluted (in shares)
Weighted average number of ordinary shares used in calculating diluted earnings per share
Investments held at FVTPL
Other
Investments Held At FVTPL [Member]
Investments held at FVTPL [Member]
Commodity derivatives - payments
Commodity Derivatives - Payments [Member]
Commodity Derivatives - Payments [Member]
Gross carrying amounts
Gross financial liabilities subject to offsetting, enforceable master netting arrangements or similar agreements
Nemo Link Limited
Nemo Link Limited [Member]
Nemo Link Limited [Member]
Included within operating profit
Included Within Operating Profit [Abstract]
Included Within Operating Profit
Floating rate
Floating interest rate [member]
Equities
Equity instruments, amount contributed to fair value of plan assets
Tax
Tax Expense (Income) on Disposal Of Assets Or Disposal Groups
Tax Expense (Income) on Disposal Of Assets Or Disposal Groups
Trade and other payables
Trade And Other Payables [Member]
Trade And Other Payables [Member]
Classes of intangible assets other than goodwill [domain]
Classes of intangible assets other than goodwill [domain]
Disclosure of associates [table]
Disclosure of associates [table]
Restrictions on asset recognised
Restrictions on asset recognised
Irrecoverable Surplus, Restrictions On Assets Recognized
Irrecoverable Surplus, Restrictions On Assets Recognized
Interest income on financial instruments:
Interest and Finance Income [Abstract]
Interest and Finance Income
Audit of the Parent Company’s individual and consolidated financial statements
Auditor's Remuneration For Audit Services, Individual And Consolidated Financial Statements
Auditor's Remuneration For Audit Services, Individual And Consolidated Financial Statements
Share-based payments
Adjustments for share-based payments
Disclosure of joint ventures [line items]
Disclosure of joint ventures [line items]
Disclosure of offsetting of financial assets and financial liabilities
Disclosure of offsetting of financial assets and financial liabilities [text block]
Classes of intangible assets and goodwill [axis]
Classes of intangible assets and goodwill [axis]
Net amount
Net financial assets subject to offsetting, enforceable master netting arrangements or similar agreements
Pre-derivative position
Pre-Derivative Position [Member]
Pre-derivative Position [Member]
Non-controlling interests
Non-controlling interests
Reserves within equity [domain]
Reserves within equity [domain]
Shares issued, number of ordinary shares, basis (in shares)
Shares Issued, Number Of Ordinary Shares, Basis
Shares Issued, Number Of Ordinary Shares, Basis
Segment consolidation items [axis]
Segment consolidation items [axis]
Pensions and other post-retirement benefits
Disclosure of employee benefits [text block]
Disclosure of analysis of other comprehensive income by item [table]
Disclosure of analysis of other comprehensive income by item [table]
Schedule of changes in intangible assets and goodwill
Disclosure of reconciliation of changes in intangible assets and goodwill [text block]
Depreciation, amortisation and impairment
Adjustments for depreciation and amortisation expense and impairment loss (reversal of impairment loss) recognised in profit or loss
Purchases
Purchases, Fair Value Measurement, Assets (Liabilities)
Purchases, Fair Value Measurement, Assets (Liabilities)
Reclassification to held for sale (note 10)
Decrease Through Reclassification To Held For Sale, Financial Assets
Decrease Through Reclassification To Held For Sale, Financial Assets
Non-controlling interests
Profit (loss), attributable to non-controlling interests
All Currencies [Domain]
All Currencies [Domain]
Equity
Equity [abstract]
Other
Other expenses, by nature
Disclosure of disaggregation of revenue from contracts with customers [table]
Disclosure of disaggregation of revenue from contracts with customers [table]
Disclosure of detailed information about financial instruments [abstract]
Disclosure of detailed information about financial instruments [abstract]
Disclosure of operating segments [abstract]
Disclosure of operating segments [abstract]
Increase (decrease) in defined benefit obligation due to reasonably possible increase (decrease) in actuarial assumption
Increase (Decrease) In Defined Benefit Obligation Due To Reasonably Possible Increase (Decrease) In Actuarial Assumption
Increase (Decrease) In Defined Benefit Obligation Due To Reasonably Possible Increase (Decrease) In Actuarial Assumption
Disclosure of fair value measurement of assets
Disclosure of fair value measurement of assets [text block]
Value of buy-in policies offset to actuarial assumption of discount rate
Value Of Buy-In Policies Offset To Actuarial Assumption Of Discount Rate [Member]
Value Of Buy-In Policies Offset To Actuarial Assumption Of Discount Rate [Member]
Prepayments
Non-current prepayments
Disclosure of joint ventures
Disclosure of interests in joint arrangements [text block]
Employer contributions
Employer contributions
Basic earnings from continuing operations
Profit (loss) from continuing operations attributable to ordinary equity holders of parent entity, used in calculating basic earnings per share
Subclassifications of assets, liabilities and equities [abstract]
Subclassifications of assets, liabilities and equities [abstract]
Included within payroll costs
Pensions And Other Post-Retirement Benefits, Payroll Costs [Abstract]
Pensions And Other Post-retirement Benefits, Payroll Costs [Abstract]
Other financing derivatives
Increase (Decrease) In Other Financing Derivatives [Roll Forward]
Increase (Decrease) In Other Financing Derivatives
Exchange adjustments
Increase (decrease) in net defined benefit liability (asset) resulting from changes in foreign exchange rates, net defined benefit liability (asset)
Reclassification to held for sale
Increase (Decrease) Through Reclassification To Held For Sale, Deferred Tax Liability (Asset)
Increase (Decrease) Through Reclassification To Held For Sale, Deferred Tax Liability (Asset)
Assumed life expectations for a retiree age 65 today: In 20 years: Males
Actuarial Assumption Of Life Expectancy After Retirement In 20 Years, Male
Actuarial Assumption Of Life Expectancy After Retirement In 20 Years, Male
Type of member [Axis]
Type Of Member [Axis]
Type Of Member [Axis]
Hedging instruments [axis]
Hedging instruments [axis]
Assets and liabilities classified as held for sale
Assets and liabilities classified as held for sale [member]
Derivative hedging instrument
Derivative Hedging Instrument [Member]
Derivative Hedging Instrument
Financial investments
Financial Investments [Member]
Financial Investments [Member]
Collateral
Restricted Balances, Collateral [Member]
Restricted Balances - Collateral [Member]
Transactions in own shares
Transactions In Own Shares
Transactions In Own Shares
Additions
Additions other than through business combinations, intangible assets other than goodwill
Derivative liabilities - non-current
Non-Current Derivative Financial Liabilities [Member]
Non-Current Derivative Financial Liabilities [Member]
Disclosure of fair value measurement of liabilities [line items]
Disclosure of fair value measurement of liabilities [line items]
Financial Instruments [Abstract]
Financial Risk Management [Abstract]
Financial Risk Management [Abstract]
ICFR Auditor Attestation Flag
ICFR Auditor Attestation Flag
Bank account and bank overdraft
Bank Account And Bank Overdraft [Member]
Bank Account and Bank Overdraft [Member]
Disclosure of asset allocations
Disclosure of fair value of plan assets [text block]
Funded obligations
Wholly or partly funded defined benefit plans [member]
Other receivables
Other non-current receivables
Schedule of provisions
Disclosure of other provisions [text block]
Increase (decrease) in defined benefit plan expense due to reasonably possible increase (decrease) in actuarial assumption
Increase (Decrease) In Defined Benefit Plan Expense Due To Reasonably Possible Increase (Decrease) In Actuarial Assumption
Increase (Decrease) In Defined Benefit Plan Expense Due To Reasonably Possible Increase (Decrease) In Actuarial Assumption
Schedule of other non-current liabilities
Schedule Of Other Non Current Liabilities Explanatory [Table Text Block]
Schedule Of Other Non Current Liabilities Explanatory [Table Text Block]
Defined contribution plan, employer matching contribution percent of gross pay
Defined Contribution Plan, Employer Matching Contribution, Percent Of Employees' Gross Pay
Defined Contribution Plan, Employer Matching Contribution, Percent Of Employees' Gross Pay
Increases due to cash received, excluding amounts recognised as revenue during the period
Increase Due To Cash Received, Excluding Amount Recognised As Revenue
Increase Due To Cash Received, Excluding Amount Recognised As Revenue
Disclosure of temporary difference, unused tax losses and unused tax credits [table]
Disclosure of temporary difference, unused tax losses and unused tax credits [table]
Amount of accretion on inflation linked liabilities
Finance Cost, Accretion On Inflation Linked Liabilities
Finance Cost, Accretion On Inflation Linked Liabilities
Country Region
Country Region
Change in value used for calculating ineffectiveness, Hedging instrument
Gain (loss) on change in fair value of hedging instrument used as basis for recognising hedge ineffectiveness
Social security costs
Social security contributions
Litigation Case [Axis]
Litigation Case [Axis]
Eastern Green Link 1 Limited
Eastern Green Link 1 Limited [Member]
Eastern Green Link 1 Limited
Auditor Firm ID
Auditor Firm ID
Share premium account
Share premium [member]
Reclassification to held for sale (note 10)
Decrease through transfer to liabilities included in disposal groups classified as held for sale, other provisions
Disclosure of contingent liabilities [abstract]
Disclosure of contingent liabilities [abstract]
Tax relief on capitalised interest
Tax Relief On Capitalised Interest
Tax Relief On Capitalised Interest
Schedule of additional information about employee, key management personnel and auditors' remuneration
Disclosure of additional information [text block]
Disclosure of disaggregation of revenue by primary geographical market and major service lines
Disclosure of disaggregation of revenue from contracts with customers [text block]
Net movements in short-term borrowings
Net movements in short-term borrowings
Cash flows from (used in) increase (decrease) in current borrowings
Schedule of capital commitments and contingent liabilities
Schedule Of Commitments And Contingencies Explanatory [Table Text Block]
Schedule Of Commitments And Contingencies Explanatory [Table Text Block]
Equity shareholders of the parent
Comprehensive income, attributable to owners of parent
Finance Income And Costs [Table]
Finance Income And Costs [Table]
Finance Income And Costs [Table]
Gas options
Commodity Derivatives - Purchase Contracts - Gas Options [Member]
Commodity Derivatives - Purchase Contracts - Gas Options
Total comprehensive income for the year from continuing operations
Comprehensive income from continuing operations
Total liabilities
Liabilities
Initial healthcare cost trend rate
Actuarial assumption of medical cost trend rates
Other
Other Product And Services [Member]
Other Product And Services
Disclosure of subsidiaries [table]
Disclosure of subsidiaries [table]
Deferred tax:
Deferred Tax Expense (Income) And Adjustments For Current Tax Of Prior Periods [Abstract]
Deferred Tax Expense (Income) And Adjustments For Current Tax Of Prior Periods [Abstract]
Debt covenants, carrying value of the bonds under covenant restriction
Debt Covenants, Bonds, Carrying Value
Debt Covenants, Bonds, Carrying Value
Purchase of own shares, employee share trusts
Purchase Of Own Shares, Employee Share Trusts, Financing Activities
Purchase Of Own Shares, Employee Share Trusts, Financing Activities
Disclosure of maturity analysis for derivative financial liabilities
Disclosure of maturity analysis for derivative financial liabilities [text block]
Disclosure of net defined benefit liability (asset) [line items]
Disclosure of net defined benefit liability (asset) [line items]
Current tax liabilities
Current tax liabilities, current
-10% change in venture capital price
Sensitivity Analysis, 10 Percent Decrease In Venture Capital Price
Sensitivity Analysis, 10 Percent Decrease In Venture Capital Price
Other movements
Increase (decrease) in net defined benefit liability (asset) resulting from other changes
Changes in environmental provisions
Income (Expense) From Changes In Environmental Provisions
Income (Expense) From Changes In Environmental Provisions
Net gains/(losses) in respect of cost of hedging
Net gains in respect of cost of hedging
Gains (Losses) On Cost Of Hedging, Before Tax
Gains (Losses) On Cost Of Hedging, Before Tax
Interest payments on borrowings
Interest Payable On Bank Borrowings, Undiscounted Cash Flows
Interest Payable On Bank Borrowings, Undiscounted Cash Flows
Other intangible assets
Description of accounting policy for intangible assets other than goodwill [text block]
Discount rate applied to cash flow projections
Discount rate applied to cash flow projections
+20 basis points change in Limited Price Inflation (LPI) market curve
Sensitivity Analysis, 20 Basis Point Change Increase Market Curve
Sensitivity Analysis, 20 Basis Point Change Increase Market Curve
Disclosure of fair value of plan assets [line items]
Disclosure of fair value of plan assets [line items]
Environmental provisions
Temporary Differences, Environmental Provisions [Member]
Temporary Differences, Environmental Provisions [Member]
Disclosure of nature and extent of risks arising from financial instruments [table]
Disclosure of nature and extent of risks arising from financial instruments [table]
Warwick Technology Park Management Company (No 2) Limited
Warwick Technology Park Management Company (No 2) Limited [Member]
Warwick Technology Park Management Company (No 2) Limited [Member]
Current liabilities
Current Liabilities [Member]
Current Liabilities [Member]
Disclosure of reserves within equity [abstract]
Disclosure of reserves within equity [abstract]
Interest payable
Interest payable
Bank loans and overdrafts
Interest Expense On Bank Loans And Overdrafts, Including Capitalised
Interest Expense On Bank Loans And Overdrafts, Including Capitalised
Interest cover ratio
Interest Cover Ratio
Interest Cover Ratio
Property, plant and equipment, capacity
Property, Plant And Equipment, Capacity
Property, Plant And Equipment, Capacity
Audit fees payable to the Parent Company’s auditor and their associates in respect of:
Audit Fees [Abstract]
Audit Fees
-10% change in venture capital price
Venture Capital Price, Ten Percent Decrease [Member]
Venture Capital Price, Ten Percent Decrease
Disclosure of financial instruments by type of interest rate [line items]
Disclosure of financial instruments by type of interest rate [line items]
Liability-matching assets
Structured Debt, Amount Contributed To Fair Value Of Plan Assets, Percentage
Structured Debt, Amount Contributed To Fair Value Of Plan Assets, Percentage
Investments held by National Grid Partners
Investments, Corporate Capital Ventures And Other [Member]
Corporate Capital Ventures And Other [Member]
Insurance company fund investments
Investments, Insurance Company Fund [Member]
Investments, Insurance Company Fund [Member]
Disposal Group, Name [Axis]
Disposal Group, Name [Axis]
Disposal Group, Name
Cash and cash equivalents
Cash And Cash Equivalents1 [Member]
Cash and Cash Equivalents [Member]
Property, plant and equipment
Property, plant and equipment, beginning balance
Property, plant and equipment, ending balance
Property, plant and equipment including right-of-use assets
Corporation tax
Current tax expense (income)
Hedging instruments
Hedging instruments [domain]
Non-adjusting events after reporting period [axis]
Non-adjusting events after reporting period [axis]
Assets held for sale
Non-current assets or disposal groups classified as held for sale
1 to 5 years
Later than one year and not later than five years [member]
Cross-currency interest rate swaps
Financing Derivatives - Cross Currency Interest Rate Swaps [Member]
Financing Derivatives - Cross Currency Interest Rate Swaps [Member]
Continuing operations, unless line item indicates otherwise [member]
Continuing operations, unless line item indicates otherwise [member]
New IFRS accounting standards and interpretations effective for the year ended 31 March 2026
Disclosure of initial application of standards or interpretations [text block]
Number of OPEB plans
Number Of Other Post-Employment Benefit Plan
Number Of Other Post-Employment Benefit Plan
Top of range
Top of range [member]
National Grid Renewables and Emerald Energy Venture LLC
National Grid Renewables And Emerald Energy Venture LLC [Member]
National Grid Renewables And Emerald Energy Venture LLC
Intangible assets and goodwill [abstract]
Intangible assets and goodwill [abstract]
Research and development expenditure
Research and development expense
Scenario [Axis]
Scenario [Axis]
Other non-current assets
Other non-current assets
Other non-current assets
National Grid Ventures
National Grid Ventures [Member]
NG Ventures [Member]
Issued during the year in lieu of dividends (in shares)
Number Of Shares Issued Scrip Dividend Recognized As Distributions To Owners
Number Of Shares Issued Scrip Dividend Recognized As Distributions To Owners
Derivative notional amount
Derivative contractual amount
Derivatives, Notional Amount
Derivatives, Notional Amount
In 3 to 4 years
Later than three years and not later than four years [member]
Schedule of exceptional items and remeasurements from continuing operations
Disclosure Of Exceptional Items And Remeasurements From Continuing Operations Explanatory [Table Text Block]
Disclosure Of Exceptional Items And Remeasurements From Continuing Operations Explanatory [Table Text Block]
Remeasurement gains/(losses) of pension assets and post-retirement benefit obligations
Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans
Diluted EPS (discontinuing) (in GBP per share)
Diluted earnings (loss) per share from discontinued operations
Derivative contracts – payments
Financing Derivatives - Payments [Member]
Financing Derivatives - Payments [Member]
Ultimate healthcare cost trend rate
Actuarial Assumption Of Ultimate Medical Cost Trend Rates
Actuarial Assumption Of Ultimate Medical Cost Trend Rates
Bank loans
Non-current portion of non-current loans received
Total items from continuing operations that will never be reclassified to profit or loss
Other comprehensive income that will not be reclassified to profit or loss, net of tax
Other operating costs
Other operating costs
Miscellaneous other operating expense
Cash and cash equivalents
Cash and cash equivalents, amount contributed to fair value of plan assets
(Credited)/charged to other comprehensive income and equity
Deferred Tax Expense (Income) Recognised In Other Comprehensive Income Or Charges (Credited) Directly To Equity
Deferred Tax Expense (Income) Recognised In Other Comprehensive Income Or Charges (Credited) Directly To Equity
Current tax:
Current Income Tax Relating To Components Of Other Comprehensive Income And Items Credited (Charged) Directly To Equity [Abstract]
Current Income Tax Relating To Components Of Other Comprehensive Income And Items Credited (Charged) Directly To Equity [Abstract]
Assets and liabilities classified as held for sale [axis]
Assets and liabilities classified as held for sale [axis]
Increase in risk variable, impact on earnings
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Increase In Risk Variable, Impact On Earnings
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Increase In Risk Variable, Impact On Earnings
Inventories and current intangible assets
Description of accounting policy for measuring inventories [text block]
Tax on items that will never be reclassified to profit or loss
Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss
Value of buy-in policies and longevity swap offset to actuarial assumption of life expectancy after retirement
Value Of Buy-In Policies And Longevity Swap Offset To Actuarial Assumption Of Life Expectancy After Retirement [Member]
Value Of Buy-In Policies And Longevity Swap Offset To Actuarial Assumption Of Life Expectancy After Retirement [Member]
Non-taxable income
Tax effect of revenues exempt from taxation
Non-current assets other than financial instruments and pension assets
Non-current assets other than financial instruments, deferred tax assets, post-employment benefit assets, and rights arising under insurance contracts
Electricity distribution plant
Electricity Distribution Plant [Member]
Electricity Distribution Plant [Member]
Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis]
Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis]
Joint ventures [axis]
Joint ventures [axis]
Net interest income adjusted for change to irrecoverable surplus
Interest Expense (Income), Defined Benefit Plans, Adjusted For Irrecoverable Surplus
Interest Expense (Income), Defined Benefit Plans, Adjusted For Irrecoverable Surplus
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
National Grid Interconnector Holdings Limited
National Grid Interconnector Holdings Limited [Member]
National Grid Interconnector Holdings Limited [Member]
Rights Issue
Increase (Decrease) Through Rights Issue
Increase (Decrease) Through Rights Issue
Borrowings by name [domain]
Borrowings by name [domain]
Present value of funded obligations
Defined benefit obligation, at present value
Additions
Additions Other Than Through Business Combinations, Investments Accounted For Using Equity Method
Additions Other Than Through Business Combinations, Investments Accounted For Using Equity Method
Currency risk
Currency risk [member]
60 – 90 days past due
Later than two months and not later than three months [member]
Trade receivables
Trade receivables [member]
Impairment
Impairment
Impairment loss (reversal of impairment loss) recognised in profit or loss
Schedule of dividends to shareholders
Disclosure Of Dividends To Shareholders [Table Text Block]
Disclosure Of Dividends To Shareholders [Table Text Block]
Total IFRS 15 revenue
Revenue from contracts with customers
Real undiscounted
Other Provisions, Undiscounted Cash Flows
Other Provisions, Undiscounted Cash Flows
New England Hydro Finance Company, Inc.
New England Hydro Finance Company, Inc. [Member]
New England Hydro Finance Company, Inc. [Member]
Exchange adjustments
Increase (decrease) through foreign exchange, financial assets
Number of distribution network
Number Of Distribution Network Operators
Number Of Distribution Network Operators
Deferred tax liabilities
Deferred tax liabilities
Change in risk variable, impact on other equity reserves
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Other Equity Reserves
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Other Equity Reserves
Tax paid
Income taxes paid (refund), classified as operating activities
Other comprehensive loss
Other comprehensive income/(loss) for the year
Other comprehensive income
Classes of liabilities [axis]
Classes of liabilities [axis]
Capital expenditure
Capital Expenditures [Member]
Capital Expenditures [Member]
Counterparties [domain]
Counterparties [domain]
Assets distributed on settlements
Decrease (Increase) In Net Defined Benefit Liability (Asset) Resulting From Assets Distributed In Respect Of Settlements
Decrease (Increase) In Net Defined Benefit Liability (Asset) Resulting From Assets Distributed In Respect Of Settlements
Reclassification to held for sale (note 10)
Decrease through classified as held for sale, intangible assets other than goodwill
Provisions
Current
Other current provisions
Past due status [domain]
Past due status [domain]
Net (decrease)/increase in cash and cash equivalents
Increase (decrease) in cash and cash equivalents before effect of exchange rate changes
Forecast
Forecast [Member]
Title of 12(b) Security
Title of 12(b) Security
Joint ventures
Joint ventures where entity is venturer [member]
Disclosure of subsidiaries [line items]
Disclosure of subsidiaries [line items]
Disclosure of fair value measurement of liabilities
Disclosure of fair value measurement of liabilities [text block]
Rights Issue
Rights Issue
Issue of equity
Borrowings, excluding lease liabilities
Bank borrowings, undiscounted cash flows
Related amounts available to be offset but not offset in statement of financial position
Amounts subject to enforceable master netting arrangement or similar agreement not set off against financial assets [abstract]
Changes in property, plant and equipment [abstract]
Changes in property, plant and equipment [abstract]
Assets
Net defined benefit asset
Unfunded obligations
Wholly unfunded defined benefit plans [member]
Hedged items [domain]
Hedged items [domain]
Adjustment for change in discount rate on decommissioning provisions (note 26)
Increase (Decrease) Through Adjustment For Change In Discount Rate On Decommissioning Provisions, Property, Plant And Equipment Including Right-Of-Use-Assets
Increase (Decrease) Through Adjustment For Change In Discount Rate On Decommissioning Provisions, Property, Plant And Equipment Including Right-Of-Use-Assets
Transfer to retained earnings
Decrease Through Reclassification To Retained Earnings
Decrease Through Reclassification To Retained Earnings
Share of post-tax results for the year
Share of profit (loss) from continuing operations of associates and joint ventures accounted for using equity method
Disclosure Of Exceptional Items [Line Items]
Disclosure Of Exceptional Items [Line Items]
Disclosure Of Exceptional Items
Tax advisory services
Auditor's Remuneration For Tax Services, Advisory
Auditor's Remuneration For Tax Services, Advisory
Depreciation charge for the year
Depreciation, property, plant and equipment including right-of-use assets
Share capital
Disclosure of issued capital [text block]
Repayment of loans
Repayment of loans
Repayments of borrowings, classified as financing activities
Subsidiaries [domain]
Subsidiaries [domain]
Adjustments for restrictions on the defined benefit asset
Movements In Restrictions On Defined Benefit Assets Recognized
Movements In Restrictions On Defined Benefit Assets Recognized
Funding arrangements of defined benefit plans [axis]
Funding arrangements of defined benefit plans [axis]
Disclosure of treasury credit risk
Disclosure of credit risk exposure [text block]
Other
Miscellaneous other provisions [member]
Raw materials and consumables
Current raw materials and current production supplies
Borrowings by name [axis]
Borrowings by name [axis]
Administration costs
Increase (decrease) in net defined benefit liability (asset) resulting from administration costs not reflected in return on plan assets
Variable Rate1 [Domain]
Variable Rate1 [Domain]
Variable Rate1
Financial investments
Increase (Decrease) In Financial Investments [Roll Forward]
Increase (Decrease) In Financial Investments [Roll Forward]
Profit after tax from discontinued operations
Total profit after tax from discontinued operations
Profit (loss) from discontinued operations
Trade and other payables
Disclosure of trade and other payables [text block]
Derivative financial assets
Non-current derivative financial assets
Schedule of share capital
Disclosure of classes of share capital [text block]
Disclosure of detailed information about hedging instruments [table]
Disclosure of detailed information about hedging instruments [table]
Shares issued, number of ordinary shares, existing shares (in shares)
Shares Issued, Number of Ordinary Shares, Existing Shares
Shares Issued, Number of Ordinary Shares, Existing Shares
Schedule of analysis of expenses by nature and payroll costs
Disclosure of expenses by nature [text block]
Borrowings
Description of accounting policy for borrowings [text block]
Accumulated impairment
Accumulated impairment [member]
Commitments and contingencies
Disclosure of commitments and contingent liabilities [text block]
Financial and other investments
Disclosure of financial instruments [text block]
Cash and cash equivalents
Increase (Decrease) In Cash And Cash Equivalents [Roll Forward]
Increase (Decrease) In Net Cash And Cash Equivalents, Net Of Bank Overdrafts [Roll Forward]
Schedule of reserves within equity
Disclosure of reserves within equity [text block]
Disclosure of detailed information about property, plant and equipment
Disclosure of detailed information about property, plant and equipment [text block]
Variable Rate1 [Axis]
Variable Rate1 [Axis]
Variable Rate [Axis]
Regulatory licenses
Licences [member]
Classes of intangible assets and goodwill [domain]
Classes of intangible assets and goodwill [domain]
Borrowings, interest rate
Borrowings, interest rate
Hedging instrument, assets
Hedging instrument, assets
Other non-cash movements
Increase (Decrease) Through Other Non-Cash Movements, Other Financing Derivatives
Increase (Decrease) Through Other Non-Cash Movements, Other Financing Derivatives
Derivative financial instruments
Disclosure of derivative financial instruments [text block]
Disclosure of effective applicable tax rate
Disclosure Of Effective Applicable Tax Rate [Table Text Block]
Disclosure Of Effective Applicable Tax Rate [Table Text Block]
Treasury shares as percent of ordinary shares
Treasury Shares As Percent Of Ordinary Shares
Treasury Shares As Percent Of Ordinary Shares
Diluted earnings from continuing operations
Profit (loss) from continuing operations attributable to ordinary equity holders of parent entity, used in calculating diluted earnings per share
Derivative term
Derivative, Term
Derivative, Term
Balance Sheet Location [Axis]
Balance Sheet Location1 [Axis]
Balance Sheet Location [Axis]
Disclosure of detailed information about intangible assets [line items]
Disclosure of detailed information about intangible assets [line items]
UK Electricity Distribution
UK Electricity Distribution [Member]
UK Electricity Distribution
Accelerated tax depreciation
Accelerated Tax Depreciation Related Temporary Differences [Member]
Accelerated Tax Depreciation Related Temporary Differences [Member]
Payroll costs
Total payroll costs from continuing operations
Employee benefits expense
Amortisation charge for the year
Amortisation, intangible assets other than goodwill
Deferred members
Deferred Members [Member]
Deferred Members [Member]
Dividend [Abstract]
Dividend [Abstract]
Dividend
Financial risk management
Description of accounting policy for financial instruments [text block]
Changes in working capital
Increase (decrease) in working capital
Total current assets
Current assets
Exchange differences reclassified to the consolidated income statement on disposal
Reclassification of foreign currency translation reserve
Reclassification of foreign currency translation reserve
Reclassification adjustments on exchange differences on translation of foreign operations, before tax
Contracted for but not provided
Contractual capital commitments
Disclosure of operating segments [table]
Disclosure of operating segments [table]
Commodity derivatives - receipts
Commodity Derivatives - Receipts [Member]
Commodity Derivatives - Receipts [Member]
Charged/(credited) to income statement
Deferred tax expense (income) recognised in profit or loss
Treasury stock, reissued (in shares)
Number Of Shares Of Treasury Stock Reissued
Number Of Shares Of Treasury Stock Reissued
National Grid Electricity Distribution
National Grid Electricity Distribution Group [Member]
National Grid Electricity Distribution Group
UK General Ledger system
UK General Ledger System [Member]
UK General Ledger System
Reclassification to held for sale (note 10)
Decrease Though Reclassification To Held For Sale, Investments Accounted For Using Equity Method
Decrease Though Reclassification To Held For Sale, Investments Accounted For Using Equity Method
Intangible assets other than goodwill, in service amount
Intangible Assets Other Than Goodwill, In Service
Intangible Assets Other Than Goodwill, In Service
Less: interest capitalised
Interest costs capitalised
Segments [axis]
Segments [axis]
Types of risks [axis]
Types of risks [axis]
The auditing of accounts of any associate of the Company
Auditor's Remuneration For Audit Services, Accounts Of Associate Companies
Auditor's Remuneration For Audit Services, Accounts Of Associate Companies
Disclosure Of Income Taxes [Line Items]
Disclosure Of Income Taxes [Line Items]
[Line Items] for Disclosure Of Income Taxes [Table]
Other post-employment liabilities
Other Post-Employment Liabilities
Other Post-Employment Liabilities
Eastern Green Link 3 Limited
Eastern Green Link 3 Limited [Member]
Eastern Green Link 3 Limited
Retirement Plans, Name [Axis]
Retirement Plans, Name [Axis]
Retirement Plans, Name [Axis]
Trade and other payables [abstract]
Sensitivities
Description Accounting Policy To Sensitivities To Assumptions [Policy Text Block]
Description Accounting Policy to Sensitivities to Assumptions [Policy Text Block]
Investments in Sunrun
Unquoted Equity Investments [Member]
Unquoted Equity Investments [Member]
Disclosure of transactions between related parties [table]
Disclosure of transactions between related parties [table]
Disposal of the UK Electricity System Operator (ESO), disposal of the UK Gas Transmission business
Description of accounting policy for non-current assets or disposal groups classified as held for sale and discontinued operations [text block]
Other fair value movements
Adjustments for fair value losses (gains)
Acquisition of financial investments
Purchase of investments other than investments accounted for using equity method
Types of hedges [axis]
Types of hedges [axis]
Derivative financial instruments
Description of accounting policy for derivative financial instruments [text block]
Current tax assets
Current tax assets, current
+100 basis points change in discount rate
Discount Rate Risk, Fifty Basis Points Increase [Member]
Discount Rate Risk, Fifty Basis Points Increase [Member]
Income taxes paid (refund) [abstract]
Tax compliance services
Auditor's Remuneration For Tax Services, Compliance
Auditor's Remuneration For Tax Services, Compliance
Disclosure of non-adjusting events after reporting period [table]
Disclosure of non-adjusting events after reporting period [table]
Par value per share (GBP per share)
Par value per share (EUR/GBP per share)
Par value per share
Property, plant and equipment
Disclosure of property, plant and equipment [text block]
Gas options
Commodity Derivatives - Gas Options [Member]
Commodity Derivatives - Gas Options [Member]
Disclosure of sensitivity analysis for actuarial assumptions [abstract]
Disclosure of sensitivity analysis for actuarial assumptions [abstract]
Defined contribution scheme costs
Post-employment benefit expense, defined contribution plans
Amendment Flag
Amendment Flag
Total equity
Components of equity [domain]
Major transformation programme
Expense of restructuring activities
Expense of restructuring activities
Equity dividends
Dividends recognised as distributions to owners
Disclosure of operating segments [line items]
Disclosure of operating segments [line items]
Transaction, separation and integration costs
Transaction, separation and integration costs
Transaction, Separation And Integration Costs
Transaction, Separation And Integration Costs
Pensions and other post-retirement benefits
Description of accounting policy for employee benefits [text block]
Adjustments in respect of prior years
Tax Effect Of Prior Year Income Taxes
Tax Effect Of Prior Year Income Taxes
Weighted average
Weighted average [member]
Temporary difference, unused tax losses and unused tax credits [axis]
Temporary difference, unused tax losses and unused tax credits [axis]
Connecticut Yankee Atomic Power Company
Connecticut Yankee Atomic Power Company [Member]
Connecticut Yankee Atomic Power Company [Member]
Utilised
Provision used, other provisions
Forward purchases of gas
Commodity Derivatives - Forward Purchases - Gas [Member]
Commodity Derivatives - Forward Purchases - Gas [Member]
Range [domain]
Range [domain]
Issuance of bonds
Major Issuance Of Bonds [Member]
Major Issuance Of Bonds
Bank deposits and other financial assets
Interest income
South West
South West [Member]
South West
Scenario [Domain]
Scenario [Domain]
Derivative financial liabilities
Disclosure of maturity analysis for derivative financial liabilities [abstract]
Amounts payable
Amounts payable, related party transactions
Treasury shares, reissued, nominal value
Treasury Shares, Reissued
Treasury Shares, Reissued
Revenue recognised that was included in the contract liability balance at the beginning of the period
Revenue that was included in contract liability balance at beginning of period
Other financing derivatives at start of year
Other financing derivatives at end of year
Other Financing Derivatives, Assets (Liabilities)
Other Financing Derivatives, Assets (Liabilities)
Expected credit loss rate
Expected credit loss rate
Non-current financial liabilities
Non-current financial liabilities
Impairment losses on financial assets
Impairment losses on financial assets
Impairment loss recognised in profit or loss, trade receivables
Additions
Additional provisions, other provisions
Non-current tax assets
Current tax assets, non-current
Address Type [Domain]
Address Type [Domain]
Distribution
Distribution [Member]
Distribution [Member]
New York
New York Segment [Member]
New York Segment
Notional amount
Notional amount
Cash flow hedge
Reserve of cash flow hedges [member]
Lease liabilities
Current lease liabilities
Energy purchase commitments
Energy Purchase Commitment, Amount
Energy Purchase Commitment, Amount
Changes in intangible assets other than goodwill [abstract]
Changes in intangible assets other than goodwill [abstract]
Cash outflow for transaction and separation costs
Payments Related To Transaction, Separation And Integration Costs
Payments Related To Transaction, Separation And Integration Costs
Other
Other Interest Rate [Member]
Other Interest Rate [Member]
Currency [Axis]
Currency [Axis]
Gross carrying amounts
Gross Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements
Gross Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements
Adjustment for change in discount rate
Increase (decrease) through change in discount rate, other provisions
Diluted earnings per share (continuing and discontinued) (in GBP pence per share)
Diluted EPS (in GBP per share)
Diluted earnings (loss) per share
Maturity [domain]
Maturity [domain]
Share capital
Description of accounting policy for issued capital [text block]
Accrued income
Current accrued income other than current contract assets
Change in risk variable, impact on net assets
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Net Assets
Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Net Assets
Reclassification to held for sale (note 10)
Decrease through classified as held for sale, right-of-use assets
Contract liabilities
Description Of Accounting Policy For Contract Liabilities [Policy Text Block]
Description of Accounting Policy For Contract Liabilities [Policy Text Block]
Share- based payments
Share-Based Payments Related Temporary Differences [Member]
Share-based Payments Related Temporary Differences [Member]
Effective tax rate – continuing operations
Average effective tax rate
Non-derivatives hedging instrument
Non-Derivative Hedging Instrument [Member]
Non-Derivative Hedging Instrument
Collateral received
Collateral held permitted to be sold or repledged in absence of default by owner of collateral, at fair value
At fair value
At fair value [member]
Schedule of earnings per share
Earnings per share [text block]
Intangible assets other than goodwill [abstract]
Counterparty Name [Axis]
Counterparty Name [Axis]
Disclosure of associates [line items]
Disclosure of associates [line items]
Commodity contract derivative liabilities
Commodity Contract Derivative Liabilities [Member]
Commodity Contract Derivative Liabilities [Member]
Disclosure of detailed information about property, plant and equipment [table]
Disclosure of detailed information about property, plant and equipment [table]
Liabilities
Net defined benefit liability
Net foreign exchange gain (loss) on financing activities
Net Foreign Exchange Gain (Loss) On Financing Activities
Net Foreign Exchange Gain (Loss) On Financing Activities
Purchases of intangible assets
Purchase of intangible assets, classified as investing activities
Entity Incorporation, State or Country Code
Entity Incorporation, State or Country Code
Foreign exchange movements
Effect Of Exchange Rate Changes On Financial Investments
Effect Of Exchange Rate Changes On Financial Investments
Reconciliation of basic to diluted average number of shares
Weighted average ordinary shares used in calculating basic and diluted earnings per share [abstract]
Finance income and costs
Description of accounting policy for finance income and costs [text block]
Transferred to profit or loss in respect of cash flow hedges
Reclassification adjustments on cash flow hedges, before tax