How green is your energy company?

You're using less gas and electricity at home, but is your energy supplier letting you down on sustainability?

Fewer firms claim to sell '100% renewable' electricity than in previous years, and those that do manage it in different ways. But it's not just about 'renewable' tariffs. Energy companies take a range of approaches to sustainability, and some are more effective than others.

In March 2026, we asked energy companies in Great Britain to tell us more about the green electricity and gas they sell to homes, as well as other sustainable practices. 

We rated 14 energy suppliers in our analysis. The most sustainable have close links to renewable generators and low greenhouse gas emissions, while also supporting their customers to use cleaner energy. Meanwhile, some energy companies have links to fossil fuel power or show little commitment to the decarbonisation of our energy usage.

Our experts regularly round up the best energy deals to make sure you get the best tariff for your household.

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Best energy companies for sustainability: Which Eco Providers for 2026

It's not always obvious what a company is really doing behind the scenes to support the transition to renewable energy and be more sustainable overall. So, in March 2026, we asked energy suppliers in Great Britain to tell us exactly how they sourced their renewable energy and how they're helping customers cut their carbon footprint. We also assessed other aspects of their sustainability.

As a result, four companies were awarded Eco Providers for Energy for 2026:

• Good Energy
• Octopus Energy.
  
• Ecotricity, 
• 100Green

All scored full marks for buying and selling renewable power and for their greenhouse gas emissions.

The table below details the results of our findings. 

How to choose a sustainable energy company

First, be clear about what you want or expect from the company you buy from. Approaches vary, so think about which of the following would most benefit you:

• Does the company say it owns renewable generation, such as solar or wind farms? Is it building new renewable generators?
• Is it upfront about where the renewable power it sells you comes from? Look for explanations of how it buys electricity (and whether it sources it directly from renewable generators, rather than just buying REGO certificates). 
• How can it help you make your home more energy efficient? Many install solar panels, batteries, heat pumps, insulation and EV chargers for customers.
• How can it help you cut carbon emissions from your day-to-day energy use? Look out for time-of-use tariffs that reward you for using power at off-peak times when the grid is powered by renewable sources.

Don’t be swayed by environmentally friendly images, designs and phrases if they’re not backed up by factual information.

How we score energy supplier sustainability

Generating, buying and selling renewable energy is a key part of energy supplier sustainability, and worth over half the points in our assessment.

But these aren't the only factors. We also looked at companies' greenhouse gas emissions, and how they help customers cut their carbon footprint, to get a fuller picture of suppliers' overall environmental impact.

We awarded points for:

• Renewable energy: Companies scored points for closer connections to renewable power sources, such as generating it themselves, building new renewable generators and buying directly from generators. More points were available where it was from generators that didn't receive government subsidies. We assessed what proportion of the electricity used by domestic customers was directly matched with renewable electricity generated in the same half hour. Points were also available for selling green gas.
• Fossil fuel links: Points were deducted for generating electricity from fossil fuels or buying directly from fossil-fuel generators. We also took into account whether a supplier's parent company does this.
• Helping customers cut carbon: Points were available for providing customers with routes to install heat pumps, solar panels, battery storage, insulation and EV chargers as these can significantly cut home emissions. We also awarded points for offering and customer uptake of time-of-use tariffs, which encourage energy use at less popular times when there is often more renewable energy in the mix. Above average SEG rates for domestic generators, such as those with solar panels, were also rewarded. 
• Greenhouse gas emissions: We assessed the emissions involved in companies' own operations and whether they could provide Scope 3 emissions (which include emissions from gas and electricity used by customers). 

Can I get cheap green energy?

We've seen some of the cheapest fixed tariffs in recent months from Eco Provider Ecotricity. 

But that's not always the case. It sometimes costs more to buy your electricity from companies that have more direct links to renewable generation. 

Many renewable generators receive government subsidies. But some energy firms buy from generators that don't have subsidies, such as smaller generators. This means that they're helping support renewable projects that might not otherwise exist, but can come at an extra cost.

Three energy companies are exempt from the price cap on default energy tariffs because they have proved to energy regulator Ofgem that they have higher costs because they support renewables,  that they go further than existing subsidies, and that customers have actively chosen them. 

They're allowed to charge more for their default tariffs, which are often among the priciest available. They are:

• 100Green
• Ecotricity
• Good Energy

Green gas is more expensive than renewable electricity and there is less of it around. 

Compare gas and electricity prices with our free independent energy comparison tool

Can I get 100% renewable electricity to my home?

Unless you generate renewable electricity yourself, such as with solar pv panels, you can't guarantee that 100% of your power comes from renewable generators. 

The source of the electricity that comes by wire into your home depends on:

• where you live
• how much renewable generation is happening across the country at the time. 

On average, around 42.1% of our electricity nationally now comes from renewable sources, with a further 16.2% generated by nuclear power.

Average UK fuel mix

1. Renewables - 42.1%
2. Natural gas - 33.3%
3. Nuclear - 16.2%
4. Coal - 5.9%
5. Other fuels - 2.5%

Source: Department for Energy Security and Net Zero's UK fuel mix; figures from April 2024 to March 2025. Its next update is due in August 2026.

If you buy a 100% renewable tariff, it does not change the electricity that comes into your home. But it does change what part of the energy market you are paying for.

Electricity used at off-peak times is more likely to come from renewable sources, as it's usually during periods of high peak demand that the National Grid needs to burn fossil fuels. Some energy companies are starting to offer tariffs that make the most of this by incentivising you to use off-peak energy at cheaper rates.

Want to start generating your own renewable electricity? Find out more about solar panels and home energy storage.

What is green gas?

Green gas is biomethane. It makes up a very small proportion of the gas in our grid – most of it is natural gas.

Biomethane is made when organic materials, such as food waste and animal manure, are broken down by bacteria in huge 'digesters' tanks without oxygen. 

The biogas produced is then purified and the CO2 is removed, turning it into biomethane. Biomethane has similar characteristics to natural gas, so it can be added to the gas grid and used in our homes. 

It can also be produced from landfill gas and the gasification of biomass. 

Biomethane is carbon neutral. Burning it releases the same amount of carbon dioxide that the organic materials it's made from absorbed when they grew so, overall, it doesn't add more CO2 to the atmosphere.

Several energy companies sell green gas alongside renewable electricity. They include:

Green gas is not piped directly into you home if you buy a tariff that includes it. The difference with a green gas tariff is that you pay extra towards the green gas added into the grid mix.

There are certificates to show where green gas was produced. They are called renewable gas guarantees of origin (RGGOs) and biomethane certificates. 

If you’re looking to cut the carbon footprint of your heating, find out more about heat pumps.

What is a renewable energy tariff?

There is no set definition of what a renewable or green tariff is, and companies take a variety of approaches. 

To make an ‘environmental claim’ about a tariff, an energy company must:

• Show that the environmental gain is because the customer chose the tariff;
• Publish its fuel mix and information about the environmental benefit of the tariff;
• Be able to prove where its renewable energy has come from, by having enough certificates.

To sell a tariff labelled as 100% renewable electricity, an energy firm must buy enough certificates for renewable energy (called Renewable Energy Guarantees of Origin or REGOs) to match what customers on the tariff use over a year.

But these certificates don’t prove that the company has generated renewable electricity itself, nor bought renewable electricity directly from a generator. Suppliers can buy them without buying the associated renewable electricity.

Energy companies take different approaches to providing 100% renewable tariffs:

• Selling renewable power from generators the company operates to match customer demand;
• Having a contract or trading deal to take the output of a renewable generator and incorporate it into a tariff;
• Matching customer consumption against renewable output via traded certificates (such as REGOs).

Many companies use a combination of these.

Additionally some companies try to match the electricity used by customers with renewable electricity generated in the same half hour as much as possible.  

Find out whether your energy company generates renewable electricity and its other sustainable practices in our energy company reviews.

Other sustainable features of energy companies

Besides how they source and sell electricity and gas, companies have other approaches to improving their sustainability. These include:

• Sustainable accreditation, such as B Corp or Vegan Society
• Encouraging sustainable behaviour through app features, energy efficiency advice or schemes
• Making charitable donations
• Participating in community or charity energy programmes (such as involvement with solar panel community projects)
• Tree planting
• Replacing company vehicles with EVs and cutting company office emissions.