Market share of Big Six domestic electricity suppliers in GB Q1 2010-Q1 2023

British Gas is the largest retail electricity supplier in Great Britain. Despite a notable decline throughout the years, it still accounted for 20 percent of the market in 2023. E.ON followed closely, with a market share of 17 percent during the same period.

 Changes in the Big Six 

  The electricity market in Great Britain has historically been controlled by a few providers, collectively known as the Big Six. These include British Gas, E.ON, SSE, EDF, Npower, and Scottish Power. However, in recent years, there have been significant changes in their composition. In January 2020, OVO Energy acquired SSE's electricity and gas distribution business, albeit continuing to sell energy under the SSE brand. Meanwhile, Npower was acquired by E.ON in 2019, turning the Big Six into a de-facto Big Five.

 Growing competition in the British electricity supply market 

In 2010, the Big Six held 100 percent of the domestic electricity supply market in the UK. In order to promote a more competitive market, the British energy regulator, Ofgem, enacted a series of market reforms aimed at increasing access for smaller players. The past decade has seen a significant number of domestic customers switching from large electricity suppliers to small and mid-tier suppliers, causing the Big Six’s market share to dip below 75 percent in 2022.