National Grid (Great Britain)

The National Grid is the high-voltage electric power transmission network supporting the UK's electricity market, connecting power stations and major substations, and ensuring that electricity generated anywhere on the grid can be used to satisfy demand elsewhere. The network serves the majority of Great Britain and some of the surrounding islands. It does not cover Northern Ireland, which is part of the Irish single electricity market.

The National Grid is a wide area synchronous grid operating at a nominal 50 hertz. Most of the physical HV parts of the grid consists of 400 kV lines as well as some 275 kV lines that collectively form a supergrid. It has several undersea interconnectors: an AC connector to the Isle of Man, and DC connectors to Northern Ireland, the Shetland Islands, the Republic of Ireland, France, Belgium, the Netherlands, Norway, and Denmark.

Since the privatisation of the Central Electricity Generating Board in 1990, the National Grid in England and Wales is owned by National Grid plc. In Scotland the grid is owned by ScottishPower Transmission in the south, and by SSE in the north. Infrastructure connecting offshore wind farms to the grid is owned by offshore transmission owners.

Since October 2024, the transmission system operator for the whole GB grid is the government-owned National Energy System Operator (NESO).