v3.26.3
Revenue (Details) - GBP (£)
£ in Millions
 6 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue £ 7,680 £ 6,761
Total other revenue 458 304
Total revenue 8,138 7,065
Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 7,680  
Total other revenue 316  
Total revenue 7,996  
Exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total revenue 142  
UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2,972 2,623
Total other revenue 195 79
Total revenue 3,167 2,702
US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 4,708 4,138
Total other revenue 263 225
Total revenue 4,971 4,363
UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,722 1,306
Total other revenue 44 100
Total revenue 1,766 1,406
UK Electricity Transmission | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,722  
Total other revenue 44  
Total revenue 1,766  
UK Electricity Transmission | Exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total revenue 0  
UK Electricity Transmission | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,722 1,306
Total other revenue 44 100
UK Electricity Transmission | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Total other revenue 0 0
UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 917 894
Total other revenue 2 2
Total revenue 919 896
UK Electricity Distribution | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 917  
Total other revenue 2  
Total revenue 919  
UK Electricity Distribution | Exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total revenue 0  
UK Electricity Distribution | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 917 894
Total other revenue 2 2
UK Electricity Distribution | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Total other revenue 0 0
New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,608 1,474
Total other revenue 22 19
Total revenue 1,630 1,493
New England | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,608  
Total other revenue 22  
Total revenue 1,630  
New England | Exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total revenue 0  
New England | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Total other revenue 0 0
New England | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,608 1,474
Total other revenue 22 19
New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 3,091 2,648
Total other revenue 16 19
Total revenue 3,107 2,667
New York | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 3,091  
Total other revenue 16  
Total revenue 3,107  
New York | Exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total revenue 0  
New York | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Total other revenue 0 0
New York | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 3,091 2,648
Total other revenue 16 19
National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 339 437
Total other revenue 154 144
Total revenue 493 581
National Grid Ventures | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 339  
Total other revenue 154  
Total revenue 493  
National Grid Ventures | Exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total revenue 0  
National Grid Ventures | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 333 423
Total other revenue (61) (38)
National Grid Ventures | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 6 14
Total other revenue 215 182
Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 3 2
Total other revenue 220 20
Total revenue 223 22
Other | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 3  
Total other revenue 78  
Total revenue 81  
Other | Exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total revenue 142  
Other | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Total other revenue 210 15
Other | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 3 2
Total other revenue 10 5
Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   1,928
Transmission | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2,310  
Transmission | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   1,293
Transmission | UK Electricity Transmission | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,706  
Transmission | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Transmission | UK Electricity Distribution | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0  
Transmission | New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   49
Transmission | New England | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 50  
Transmission | New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   163
Transmission | New York | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 221  
Transmission | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   423
Transmission | National Grid Ventures | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 333  
Transmission | Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Transmission | Other | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0  
Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   4,758
Distribution | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 5,296  
Distribution | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Distribution | UK Electricity Transmission | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0  
Distribution | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   860
Distribution | UK Electricity Distribution | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 882  
Distribution | New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   1,421
Distribution | New England | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,553  
Distribution | New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   2,477
Distribution | New York | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2,861  
Distribution | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Distribution | National Grid Ventures | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0  
Distribution | Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Distribution | Other | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0  
Generation    
Revenue from Contracts with Customers [line items]    
Total other revenue   177
Generation | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total other revenue 211  
Generation | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total other revenue   0
Generation | UK Electricity Transmission | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total other revenue 0  
Generation | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total other revenue   0
Generation | UK Electricity Distribution | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total other revenue 0  
Generation | New England    
Revenue from Contracts with Customers [line items]    
Total other revenue   (1)
Generation | New England | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total other revenue 0  
Generation | New York    
Revenue from Contracts with Customers [line items]    
Total other revenue   0
Generation | New York | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total other revenue 0  
Generation | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total other revenue   178
Generation | National Grid Ventures | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total other revenue 211  
Generation | Other    
Revenue from Contracts with Customers [line items]    
Total other revenue   0
Generation | Other | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total other revenue 0  
Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   75
Total other revenue   127
Other | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 74  
Total other revenue 105  
Other | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   13
Total other revenue   100
Other | UK Electricity Transmission | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 16  
Total other revenue 44  
Other | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   34
Total other revenue   2
Other | UK Electricity Distribution | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 35  
Total other revenue 2  
Other | New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   4
Total other revenue   20
Other | New England | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 5  
Total other revenue 22  
Other | New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   8
Total other revenue   19
Other | New York | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 9  
Total other revenue 16  
Other | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   14
Total other revenue   (34)
Other | National Grid Ventures | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 6  
Total other revenue (57)  
Other | Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   2
Total other revenue   £ 20
Other | Other | Before exceptional items and remeasurements    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 3  
Total other revenue £ 78