v3.24.1.1.u2
Property, plant and equipment - Disclosure of useful economic lives of property, plant and equipment (Details)
 12 Months Ended
Mar. 31, 2024
Weighted average | Freehold and leasehold buildings  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 38 years
Weighted average | Electricity transmission plant and wires  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 32 years
Weighted average | Electricity distribution plant  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 46 years
Weighted average | Electricity generation plant  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 10 years
Weighted average | Interconnector plant and other  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 31 years
Weighted average | Gas plant – mains, services and regulating equipment  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 53 years
Weighted average | Gas plant – storage  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 18 years
Weighted average | Gas plant – meters  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 24 years
Weighted average | Motor vehicles and office equipment  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 3 years
UK | Bottom of range | Electricity distribution plant  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 14 years
UK | Bottom of range | Interconnector plant and other  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 5 years
UK | Bottom of range | Gas plant – storage  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 5 years
UK | Top of range | Freehold and leasehold buildings  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 60 years
UK | Top of range | Electricity transmission plant and wires  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 100 years
UK | Top of range | Electricity distribution plant  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 99 years
UK | Top of range | Interconnector plant and other  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 70 years
UK | Top of range | Gas plant – storage  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 20 years
UK | Top of range | Motor vehicles and office equipment  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 50 years
US | Bottom of range | Electricity transmission plant and wires  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 10 years
US | Bottom of range | Electricity distribution plant  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 5 years
US | Bottom of range | Electricity generation plant  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 10 years
US | Bottom of range | Interconnector plant and other  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 5 years
US | Bottom of range | Gas plant – mains, services and regulating equipment  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 25 years
US | Bottom of range | Gas plant – storage  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 20 years
US | Bottom of range | Gas plant – meters  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 14 years
US | Top of range | Freehold and leasehold buildings  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 100 years
US | Top of range | Electricity transmission plant and wires  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 85 years
US | Top of range | Electricity distribution plant  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 85 years
US | Top of range | Electricity generation plant  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 93 years
US | Top of range | Interconnector plant and other  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 37 years
US | Top of range | Gas plant – mains, services and regulating equipment  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 95 years
US | Top of range | Gas plant – storage  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 60 years
US | Top of range | Gas plant – meters  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 45 years
US | Top of range | Motor vehicles and office equipment  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful economic life, property, plant and equipment 26 years