Green Energy Supplier Comparison UK: Who Is Genuinely Green in 2026?

What is a green energy supplier and how do you compare them?

A green energy supplier sells electricity matched 100% by renewable generation — wind, solar, hydro or biomass. To compare green suppliers in the UK, look beyond the label: check how much power they buy directly from renewable generators, whether they offer green gas, their Which? eco rating, and how their tariffs compare with the Ofgem price cap.

The distinction matters because UK rules still allow a supplier to market a tariff as “green” while buying most of its power from the wholesale market — including fossil fuel generation — as long as it covers customer demand with cheap certificates. Understanding that loophole is the key to any honest green energy comparison.

How to compare green energy suppliers in 5 steps

Before switching, run any supplier through these five checks — they separate the genuinely green companies from the marketing:

1. 1
   Check the fuel mix disclosure. Every UK supplier must publish where its electricity comes from. A genuinely green supplier reports 100% renewable electricity — and can tell you the split between wind, solar, hydro and biomass.
2. 2
   Ask how the power is bought. The greenest suppliers buy electricity directly from renewable generators through power purchase agreements, or generate it themselves. The weakest simply buy certificates (see the REGO loophole below).
3. 3
   Look at the gas. Electricity is the easy part — gas is where suppliers differ most. Only 100Green sells 100% green gas (biomethane); most others sell standard fossil gas, sometimes with carbon offsetting.
4. 4
   Check independent eco ratings. The Which? sustainability analysis and Uswitch green accreditations audit suppliers’ claims every year — for 2026, only four companies made the Which? Eco Provider grade.
5. 5
   Compare prices against the Ofgem cap. The price cap for July–September 2026 is £1,663 per year for a typical household (26.11p/kWh for electricity, 7.33p/kWh for gas). Green fixed tariffs are often competitive with it — being green no longer means paying a premium.

The REGO loophole: why some “green” tariffs are greenwashing

In the UK, every megawatt-hour of renewable electricity earns a REGO certificate (Renewable Energy Guarantee of Origin). The problem: REGOs can be sold separately from the electricity itself. A supplier can buy all its power from the wholesale market — gas plants included — then buy enough spare REGOs to label its tariff “100% renewable”. Covering a typical household costs the supplier just a few pounds a year.

The practice is now widely criticised as greenwashing. The UK government has pledged to tighten the rules on how tariffs are marketed, OVO stopped buying REGOs altogether in 2023, and Good Energy and ScottishPower have jointly called on the regulator to close the loophole. Reform, however, is still pending.

Green energy supplier comparison table (2026)

The table below only includes suppliers that are trading and verified in 2026. All four Which? Eco Providers appear, plus So Energy as a larger renewable-electricity option. Price positions change with each tariff release, so always compare live quotes against the Ofgem cap:

Sources: Which? sustainability analysis 2026, 100Green, So Energy. Choosing one of these suppliers is one of the most effective ways to cut your household carbon footprint — most of the UK’s renewable power now comes from wind energy, which was the country’s largest source of electricity in 2025.

What happened to Pure Planet, Bulb and the other green suppliers?

If this page looks very different from the version published in 2021, that is because the UK energy market went through a historic shake-out. When wholesale gas prices exploded in late 2021, around 30 suppliers went bust within about a year — including several of the best-known green brands:

• Pure Planet ceased trading in October 2021 after BP withdrew its backing. Ofgem moved its 235,000 customers to Shell Energy — which was itself bought by Octopus Energy in December 2023, so former Pure Planet customers are now with Octopus;
• Bulb Energy, once the UK’s biggest green challenger with 1.5 million customers, entered special administration in November 2021 and was taken over by Octopus Energy in late 2022;
• Together Energy, Colorado Energy and Outfox the Market’s green rivals were among the many smaller names that either collapsed or exited the household market during the crisis.

The survivors changed too. Good Energy was delisted from the stock market in April 2025 after a £99.4 million takeover by Dubai-based smart-grid group Esyasoft — but it continues to trade under the same brand, from the same Chippenham base, with the same 100% renewable model. Green Energy UK rebranded as 100Green and is thriving: it was named a Which? Recommended Provider for 2026. And Ecotricity, Britain’s first green supplier, is still independent and still building its own wind and solar capacity.

Our UK green supplier guides

We keep dedicated guides for the green suppliers we have tracked since 2021 — including one that no longer exists, kept as a historical record for former customers:

To go further, read our guides to renewable energy and the energy transition — and if you want to cut your bills as well as your emissions, see our tips to reduce your electricity bill.