Who are the best green energy suppliers in the UK? (2026)

Who are the best green energy suppliers?

The UK energy market has shifted heavily towards renewable power. With renewable sources providing 44% of Britain’s electricity in 2025, finding a green energy supplier is much easier than it used to be. However, not all green tariffs are the same. Some suppliers actively build wind farms and buy power directly from local generators, while others buy cheap fossil-fuel energy and simply buy certificates to label it as green.^[1]

The cost of going green has also changed. You no longer have to pay a premium to power your home with renewable electricity. Many of the best green fixed tariffs cost less than the standard Ofgem price cap, which sits at £1,663 a year for a typical dual-fuel home. On top of this, new regulations are changing how suppliers can advertise their green credentials, making it harder for companies to use carbon offsetting to hide behind a green label.

In this guide, we look at the suppliers offering the most genuine green energy, how they source their electricity and gas, and how much they currently charge.

What makes an energy supplier truly green?

Before comparing suppliers, it helps to know how they back up their green claims. When you sign up for a green tariff, the electricity flowing into your home is exactly the same as your neighbour's. All power mixes together in the National Grid. A green tariff simply means your supplier promises to put enough renewable energy back into the grid to match what you take out.

How they do this is what sets the best green suppliers apart from the rest.

The REGO certificate system has faced heavy criticism. Because certificate prices crashed to roughly 77p per megawatt-hour, some suppliers buy standard wholesale power and add cheap REGOs to market their tariffs as '100% renewable'. If you want to make a real difference to the UK's green energy supply, look for suppliers that buy directly from renewable generators or build their own wind and solar farms.

Gas is another major issue. Genuine green gas (biomethane) is very expensive and hard to produce in large amounts. To get around this, many suppliers historically offered 'carbon-offset gas'. In the UK, consumer-protection and advertising rules require environmental claims to be clear and substantiated. Suppliers should not present fossil gas as green or climate neutral without a robust basis for the claim.^[1]

Octopus Energy: Best for smart technology and value

Octopus Energy is the UK's largest energy supplier, with more than 8 million customers and roughly a quarter of the market. It is one of only four companies to hold a current 'Which? Eco Provider' endorsement. Octopus provides 100% zero-carbon electricity as standard across all its tariffs, backed by its own massive investments in green generation. The company operates enough zero-carbon energy to power 4 million homes and buys from hundreds of independent green producers across the country.

Octopus does not offer a green gas tariff. It used to offer a 'Supergreen' tariff that offset gas usage, but it stopped this to focus entirely on moving homes away from gas. Instead of trying to source rare biomethane or relying on offsets, Octopus focuses on electric heat pumps, solar panels, and home batteries like its own Nook Cube and Nook Colossus systems.

What sets Octopus apart is its smart time-of-use tariffs. Tariffs like Agile Octopus and Intelligent Octopus Go offer incredibly cheap electricity rates when wind generation is high and grid demand is low. For homes with electric vehicles or heat pumps, these tariffs can cut bills drastically while using the greenest power on the grid.

Octopus is also highly competitive on price. Its standard 12-month fixed tariff currently charges 24.25p per kWh for electricity and 6.56p per kWh for gas, making it one of the cheapest ways to get 100% zero-carbon electricity without paying a premium.

Ecotricity: Best for building new renewable generation

Ecotricity is one of the UK's oldest green energy suppliers, having started in 1995. It has around 200,000 customers and operates with a very clear mission: it uses customer bill money to build new wind and solar farms. It has built 24 wind parks and three sun parks across the country, providing enough power for over 60,000 homes.

The company provides 100% zero-carbon electricity, with a large chunk generated by its own sites and the rest backed by green certificates. It also holds a unique 'Vegan energy' certification from The Vegan Society, meaning no animal byproducts are used in its biomass or anaerobic digestion processes.^[1][2][3][4]

For gas, Ecotricity supplies about 1% green gas from its own green gas mills, while the remaining 99% is standard natural gas. It has historically offset these emissions through carbon reduction schemes. However, with the new ECGT regulations banning 'climate neutral' claims based on offsets, Ecotricity and other suppliers are having to change how they talk about offset gas.

Because Ecotricity actively builds infrastructure, its prices are higher than average. Its Standard Variable Green Tariff currently charges 30.63p per kWh for electricity and 7.86p per kWh for gas. You pay a premium, but that money directly funds new green energy projects in the UK.

100Green: Best for 100% green gas

100Green (formerly GEUK) is a smaller supplier that stands out for one major reason: it is the only supplier in the UK to offer 100% green gas. While other companies rely on offsets or smaller biomethane proportions, 100Green matches customers’ gas use with biomethane produced through anaerobic digestion, which turns organic waste into usable gas.

The supplier does not build its own wind farms or gas mills. Instead, it works with independent generators across the UK to buy the green gas and electricity it needs. Its electricity is 100% zero-carbon and backed by REGO certificates.

Because 100Green commits to sourcing 100% biomethane, which is very expensive to produce, it is exempt from the standard Ofgem price cap. This means its variable tariffs can cost more than the market average. However, its fixed deals can still be competitive. Its Exclusive Spring 12-month fix currently charges 21.38p per kWh for electricity and 6.90p per kWh for gas, with no exit fees.

If your home relies on gas heating and you want to cut your carbon footprint without installing a heat pump, 100Green is the only supplier that can give you a fully green gas supply.

Good Energy: Best for supporting independent generators

Good Energy is another pioneer of the green energy market, starting in 1999. Like Ecotricity, it has roughly 200,000 customers and holds a 'Which? Eco Provider' endorsement. Good Energy guarantees 100% zero-carbon electricity, but rather than building its own wind farms, it focuses on buying power directly from independent UK generators.

The company has Power Purchase Agreements with over 3,000 renewable generators across the country, ranging from large solar farms to small local hydro projects. By buying power directly from them, Good Energy gives these sites the financial backing they need to keep running, making it a much deeper shade of green than suppliers who just buy cheap REGO certificates.

For gas, Good Energy supplies 10% genuine green gas (biogas), which is a much higher mix than most of the market. The remaining 90% is standard gas that it offsets through global zero-carbon projects.

Good Energy prices its tariffs competitively for a deep green supplier. Its 12-month fixed tariff currently charges 23.07p per kWh for electricity and 6.43p per kWh for gas, though it does carry a £150 exit fee per fuel if you leave the contract early.

OVO Energy: Best for electric vehicle owners

OVO Energy is one of the UK's largest suppliers, with around 5 million customers. In May 2026, E.ON announced plans to buy OVO, a move that will combine two of the biggest names in the market once the deal completes.

Unlike the other suppliers on this list, OVO does not offer 100% zero-carbon electricity as standard across all its tariffs. To get 100% renewable electricity and a gas add-on that includes 10% green gas, you have to add a 'Greener Energy' upgrade to your tariff. This upgrade ensures your electricity comes from UK renewable generators and includes a £20 annual contribution to help build new green projects. The gas side of the upgrade provides 10% green gas and 90% carbon-offset gas.

Where OVO excels is in its specialist tariffs for electric vehicle owners. Its Charge Anytime add-on allows EV drivers to charge their cars at an incredibly low rate by letting OVO smart-charge the vehicle when the grid has spare renewable power.

OVO's standard 1-year fixed tariff currently charges 26.47p per kWh for electricity and 7.44p per kWh for gas, with a £100 exit fee per fuel.

How green energy costs compare

The price of green energy has fallen significantly since the height of the energy crisis. You no longer have to assume that choosing a green supplier means paying higher bills. Many standard 100% renewable electricity tariffs are priced below the Ofgem price cap.

Government changes have also helped lower costs. From April 2026, suppliers removed ECO and Great British Insulation Scheme costs from domestic tariffs following scheme closure, while government funding covered 75% of domestic Renewables Obligation costs. On top of this, the government is cutting VAT on domestic electricity bills from 5% to 0% for an initial six months starting in October, which will lower the final cost of all the electricity rates shown below.

As the table shows, 100Green and Good Energy currently offer very competitive fixed rates, while Octopus Energy remains consistently cheap across its fixed and flexible deals. Ecotricity is the most expensive option, but this reflects its model of using customer funds to build physical wind and solar farms.

How to choose the right green supplier for your home

Because there is no single definition of a green supplier, the right choice depends entirely on what you want to achieve and how much you are willing to spend.

If you want the absolute cheapest 100% zero-carbon electricity, Octopus Energy is the most practical choice. It offers excellent customer service, fair prices, and smart tariffs that reward you for shifting your usage away from peak times.

If you rely on a gas boiler and want to stop burning fossil fuels without installing a heat pump, 100Green is your only real option. Its 100% biomethane gas tariff is completely unique in the UK market, though it can cost more than a standard dual-fuel deal.

If your main goal is to support the construction of new renewable energy sites in the UK, Ecotricity and Good Energy are the clearest choices. They do not rely on cheap REGO certificates, ensuring that the money you pay directly funds independent green generators.