v3.25.3
Revenue (Details) - GBP (£)
£ in Millions
 6 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue £ 6,761 £ 7,613
Total other revenue 304 348
Total revenue from continuing operations 7,065 7,961
UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2,623 3,736
Total other revenue 79 19
Total revenue from continuing operations 2,702 3,755
US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 4,138 3,877
Total other revenue 225 329
Total revenue from continuing operations 4,363 4,206
UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,306 1,132
Total other revenue 100 50
Total revenue from continuing operations 1,406 1,182
UK Electricity Transmission | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,306 1,132
Total other revenue 100 50
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 894 1,162
Total other revenue 2 2
Total revenue from continuing operations 896 1,164
UK Electricity Distribution | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 894 1,162
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
UK Electricity System Operator    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   1,012
Total other revenue   0
Total revenue from continuing operations 0 1,012
UK Electricity System Operator | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   1,012
Total other revenue   0
UK Electricity System Operator | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Total other revenue   0
New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,474 1,518
Total other revenue 19 27
Total revenue from continuing operations 1,493 1,545
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 1,474 1,518
Total other revenue 19 27
New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2,648 2,315
Total other revenue 19 26
Total revenue from continuing operations 2,667 2,341
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 2,648 2,315
Total other revenue 19 26
National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 437 473
Total other revenue 144 151
Total revenue from continuing operations 581 624
National Grid Ventures | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 423 430
Total other revenue (38) (38)
National Grid Ventures | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 14 43
Total other revenue 182 189
Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2 1
Total other revenue 20 92
Total revenue from continuing operations 22 93
Other | UK    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Total other revenue 15 5
Other | US    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2 1
Total other revenue 5 87
Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,928 1,764
Transmission | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,293 1,116
Transmission | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Transmission | UK Electricity System Operator    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   46
Transmission | New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 49 46
Transmission | New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 163 126
Transmission | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 423 430
Transmission | Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 4,758 4,763
Distribution | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Distribution | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 860 1,113
Distribution | UK Electricity System Operator    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Distribution | New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 1,421 1,468
Distribution | New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2,477 2,181
Distribution | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 0
Distribution | Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 0 1
System Operator    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   966
System Operator | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
System Operator | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
System Operator | UK Electricity System Operator    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   966
System Operator | New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
System Operator | New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
System Operator | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
System Operator | Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Generation    
Revenue from Contracts with Customers [line items]    
Total other revenue 177 191
Generation | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total other revenue 0 0
Generation | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total other revenue 0 0
Generation | UK Electricity System Operator    
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) 0
Generation | New York    
Revenue from Contracts with Customers [line items]    
Total other revenue 0 0
Generation | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total other revenue 178 191
Generation | Other    
Revenue from Contracts with Customers [line items]    
Total other revenue 0 0
Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 75 120
Total other revenue 127 157
Other | UK Electricity Transmission    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 13 16
Total other revenue 100 50
Other | UK Electricity Distribution    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 34 49
Total other revenue 2 2
Other | UK Electricity System Operator    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue   0
Total other revenue   0
Other | New England    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 4 4
Total other revenue 20 27
Other | New York    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 8 8
Total other revenue 19 26
Other | National Grid Ventures    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 14 43
Total other revenue (34) (40)
Other | Other    
Revenue from Contracts with Customers [line items]    
Total IFRS 15 revenue 2 0
Total other revenue £ 20 £ 92