British Gas is the UK’s biggest domestic energy supplier (which has just announced another round of huge price hikes). It also operates the Sainsbury’s Energy brand.
However, British Gas is actually a subsidiary of Centrica, which was formed following a demerger from British Gas plc back in 1997.
Centrica is UK-owned and based.
EDF Energy is a subsidiary of the French Government-owned energy company EDF (Électricité de France) Group. Over the years it has bought UK energy companies London Electricity, SWEB, Seeboard and British Energy.
EDF was founded in 1946 and became a public company in 2004.
E.ON is a German-owned group formed from the merger of German companies VEBA and VIAG. The group bought UK energy company Powergen back in 2002 but it wasn’t until 2007 that its UK energy operations were renamed E.ON.
Npower is a subsidiary of German energy company RWE Group. It was bought in 2002, having evolved out of National Power, later renamed npower, which had bought the likes of Calortex, Independent Energy and Midlands Electricity following privatisation.
ScottishPower is a subsidiary of Spanish company Iberdrola, who bought it in 2006. The company was formed in 1990 from the South of Scotland Electricity Board. It later bought Manweb, the energy company supplying Merseyside and North Wales.
SSE (formerly known as Scottish and Southern Energy) was formed in 1998 following the merger of Scottish Hydro Electric and Southern Electric.
In 2000, it bought SWALEC and it also owns Atlantic and Airtricity. It operates those brands plus Scottish Hydro and Southern Electric as subsidiaries of the main SSE group.