The Big 6 UK energy suppliers
Six suppliers hold most UK household accounts: Octopus Energy, British Gas, E.ON Next, OVO Energy, EDF and ScottishPower. The old "Big Six" was a different list (the incumbents privatised in the 1990s). This is the list that matters in 2026, after Octopus overtook British Gas and absorbed Bulb and Shell, and after E.ON, OVO and ScottishPower each swallowed a former incumbent. Here is who owns each one, what they do well, and where they land in our independent scoring.
Octopus Energy
Now the largest UK household supplier, after taking on Bulb and Shell Energy customers. Known for smart tariffs like Agile and Intelligent Octopus Go, strong service scores, and the Kraken platform it licenses worldwide. Also supplies Co-op Energy, M&S Energy and London Power.
See profile & score →British Gas
The largest legacy supplier, owned by Centrica, with the biggest engineer and heat-pump install network. Strong parent balance sheet, but complaint volumes run high for its size and it carries the largest recent fairness penalty of the group.
See profile & score →E.ON Next
The household brand of E.ON UK, running on the same Kraken platform as Octopus. Wide tariff range including EV, heat pump and a wholesale tracker, backed by a large European parent. Also supplies Sainsbury's Energy and the npower customer brand.
See profile & score →OVO Energy
The Bristol independent that scaled up by buying SSE's retail arm in 2020. EV and export options, a growing smart-home and flexibility range, and its own PAYG brand Boost. E.ON has agreed to buy OVO, a deal that has not yet completed.
See profile & score →EDF Energy
The UK arm of France's state-owned EDF, with a large low-carbon generation fleet, including nuclear, behind it. Stable and established, with EV tariffs, though its app and digital experience trail the leaders.
See profile & score →ScottishPower
Owned by the Spanish utility Iberdrola, with a 100% renewable generation claim and green fixed deals. Well capitalised, but customer service is a recurring weak point in independent ratings.
See profile & score →How the Big 6 became this Big 6
Consolidation, not competition alone
The 2021 to 2022 energy crisis pushed 30-odd suppliers out of the market. Their customers were moved to survivors under Ofgem's Supplier of Last Resort process. Octopus took on Bulb, OVO had already taken SSE, and E.ON, ScottishPower and EDF each hold former incumbents. Today's Big 6 is as much a product of failure and rescue as of winning customers head to head.
White-label brands sit on top of them
Several familiar names are not separate suppliers at all. Co-op Energy, M&S Energy and London Power run on Octopus's licence; Sainsbury's Energy and npower run on E.ON Next; Boost is OVO's prepayment brand. We rank the licensed supplier behind the brand, not the label, so the rankings stay comparable. Each Big 6 profile lists the brands it operates.