The Big Six were the United Kingdom's largest retail suppliers of gas and electricity, who dominated the market following liberalisation in the late 1990s.
[1] By the third quarter of 2019, after efforts by the regulator Ofgem to promote competition, their combined share in Great Britain was 70% for electricity supply and 69% for gas.
[2][3] The purchase of SSE's retail business in January 2020 by OVO Energy, a competitor founded in 2009, marked the end of the original Big Six.
[9] Just after the failed SSE-Npower merger in late 2018, it was reported that a consolidation to the Big Five would still occur, as Npower would be acquired by default by E.ON due to the already-planned asset swap by the respective German parents, Innogy and E.ON.
[11] In December 2014, Utility Warehouse, part of FTSE 250-listed company Telecom Plus[12] became the UK's biggest independent energy supplier through a £218m deal to buy 770,000 existing customers from npower.
[20] By January 2019, ten[21] small energy suppliers had ceased trading or been taken over by others, and others followed similar paths until the market turbulence in the autumn of 2021.
Bulb was placed in "special administration" and the UK government undertook to cover its losses while a sale or restructuring was organised, with a potential cost to taxpayers of £1.7 billion.