Energy market faces test of competition after E.ON-OVO deal

9 October 2026

Three energy suppliers will account for 74% of Great Britain’s domestic electricity and gas market following E.ON’s acquisition of OVO, according to analysis by Cornwall Insight.

The Competition and Markets Authority has cleared the takeover, leaving Octopus Energy as the largest supplier, followed by E.ON and British Gas.

Cornwall Insight’s Domestic Energy Market Share Survey puts Octopus Energy’s share at 26% of household electricity and gas accounts, with E.ON holding 25% and British Gas 23%. The figures count electricity and gas accounts separately, meaning households supplied with both fuels are counted twice.

The five largest suppliers, including EDF and Scottish Power, will account for 90% of the market following the deal.

The concentration of market share comes after high wholesale energy prices drove many smaller suppliers out of business from 2020 onwards. Switching rates have also remained below pre-2020 levels, with the price cap among the factors affecting the market.

Tom Goswell, energy supply lead at Cornwall Insight, says:

“The big six have become the big three, and there have been questions raised over how this will impact household choice and the health of the market. Larger suppliers do bring with them a degree of stability, and after around 30 firms dropped out of the market, leaving customers wondering who would be sending their next bill, stability is not something to dismiss lightly. They also have the scale to invest in tariffs smaller companies often struggle to offer, such as deals built around electric cars or cheaper power at off-peak times.

“The concern with fewer suppliers is that the pressure to compete eases off, taking with it some of the incentive to keep prices low and offer something different. The big suppliers have the resources to give people real choice, and the test over the next few years will be whether households who shop around find a genuine range of deals waiting for them rather than three versions of the same thing.”