v3.26.3
Segmental analysis - Schedule of revenue by segment (Details) - GBP (£)
£ in Millions
 6 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Disclosure of operating segments [line items]    
Total revenue £ 8,138 £ 7,065
Exceptional items and remeasurements    
Disclosure of operating segments [line items]    
Total revenue 142  
UK    
Disclosure of operating segments [line items]    
Total revenue 3,167 2,702
US    
Disclosure of operating segments [line items]    
Total revenue 4,971 4,363
UK Electricity Transmission    
Disclosure of operating segments [line items]    
Total revenue 1,766 1,406
UK Electricity Transmission | Exceptional items and remeasurements    
Disclosure of operating segments [line items]    
Total revenue 0  
UK Electricity Distribution    
Disclosure of operating segments [line items]    
Total revenue 919 896
UK Electricity Distribution | Exceptional items and remeasurements    
Disclosure of operating segments [line items]    
Total revenue 0  
New England    
Disclosure of operating segments [line items]    
Total revenue 1,630 1,493
New England | Exceptional items and remeasurements    
Disclosure of operating segments [line items]    
Total revenue 0  
New York    
Disclosure of operating segments [line items]    
Total revenue 3,107 2,667
New York | Exceptional items and remeasurements    
Disclosure of operating segments [line items]    
Total revenue 0  
National Grid Ventures    
Disclosure of operating segments [line items]    
Total revenue 493 581
National Grid Ventures | Exceptional items and remeasurements    
Disclosure of operating segments [line items]    
Total revenue 0  
Other    
Disclosure of operating segments [line items]    
Total revenue 223 22
Other | Exceptional items and remeasurements    
Disclosure of operating segments [line items]    
Total revenue 142  
Operating segments    
Disclosure of operating segments [line items]    
Total revenue 8,224 7,130
Operating segments | UK Electricity Transmission    
Disclosure of operating segments [line items]    
Total revenue 1,823 1,443
Operating segments | UK Electricity Distribution    
Disclosure of operating segments [line items]    
Total revenue 922 901
Operating segments | New England    
Disclosure of operating segments [line items]    
Total revenue 1,630 1,493
Operating segments | New York    
Disclosure of operating segments [line items]    
Total revenue 3,107 2,667
Operating segments | National Grid Ventures    
Disclosure of operating segments [line items]    
Total revenue 516 601
Operating segments | Other    
Disclosure of operating segments [line items]    
Total revenue 226 25
Operating segments | Other | Exceptional items and remeasurements    
Disclosure of operating segments [line items]    
Total revenue 142  
Sales between segments    
Disclosure of operating segments [line items]    
Total revenue (86) (65)
Sales between segments | UK Electricity Transmission    
Disclosure of operating segments [line items]    
Total revenue (57) (37)
Sales between segments | UK Electricity Distribution    
Disclosure of operating segments [line items]    
Total revenue (3) (5)
Sales between segments | New England    
Disclosure of operating segments [line items]    
Total revenue 0 0
Sales between segments | New York    
Disclosure of operating segments [line items]    
Total revenue 0 0
Sales between segments | National Grid Ventures    
Disclosure of operating segments [line items]    
Total revenue (23) (20)
Sales between segments | Other    
Disclosure of operating segments [line items]    
Total revenue £ (3) £ (3)