The most sustainable energy suppliers for 2024
We've assessed energy companies on a range of sustainability criteria. Three of them were named Which? Eco Providers for energy in 2024.
Two energy providers – Ecotricity and Good Energy – hold the title for the fourth year in a row. Octopus Energy is an Eco Provider for the second time.
At the other end of the spectrum, two gas and electricity suppliers scored zero points in our assessment.
Energy companies approach renewable energy and sustainability in different ways. Some have supported and generated renewable power for decades, some help customers cut their carbon footprint in other ways and take steps to reduce their company emissions. Others still aren't doing much towards decarbonising our energy grid.
When we surveyed people responsible for choosing their household's energy supplier, two thirds told us that a company's sustainability credentials were important to them in making their decision.*
But it can be tricky to separate the facts from the marketing spiel – which is where our behind-the-scenes assessment comes in.
Find out how your provider compares and the differences between green energy suppliers.
Which? Eco Providers for 2024: Ecotricity, Good Energy and Octopus Energy
We assessed 17 energy suppliers on a range of sustainability criteria, based on information they shared with us in August 2024, alongside their latest fuel mix.
All three Eco Providers score full marks for buying and selling renewable power and greenhouse gas emissions.
- Octopus Energy generates renewable power from solar, onshore and offshore wind, and also buys it directly from generators. It has an extensive choice of flexible time-of-use tariffs and among the more generous solar expert rates. It installs a range of low-carbon tech for customers and says it's made it possible to install and run a heat pump for a similar cost to a gas boiler.
- Ecotricity generates electricity from wind and solar and invests its profits into building more renewable generation. It calls this programme 'bills into mills'. Since 1995 it has built 24 wind parks and recently completed two new solar parks. It's one of just four firms that sells green gas (biomethane).
- Good Energy buys enough electricity from renewable generators to cover all of its customers' use, matching over 90% of it on a half-hourly basis. It buys much from small-scale generators that aren't supported by government subsidies, meaning that it's supporting those which might not otherwise exist. As for gas, 10% of what it sells is green. Its solar export rates are generous.
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How sustainable is my energy supplier?
Here's how energy companies scored in our assessment. Swipe or scroll right to see the breakdown of score in full.
| Eco Provider | Overall % score | Buying and selling renewable power (max 7) | Renewable generation (max 3) | Fossil fuel links (max 0, min -3) | Sells green gas (max 2) | TOU and SEG rate products (max 3) | Low carbon installations (max 2) | Greenhouse gas emissions (max 3) | |
|---|---|---|---|---|---|---|---|---|---|
| Octopus Energy* | Yes | 90% | 7 | 3 | 0 | 0 | 3 | 2 | 3 |
| Ecotricity | Yes | 85% | 7 | 3 | 0 | 1 | 2 | 1 | 3 |
| Good Energy | Yes | 85% | 7 | 0 | 0 | 2 | 3 | 2 | 3 |
| 100Green | 70% | 7 | 0 | 0 | 2 | 3 | 0 | 2 | |
| E.ON Next** | 70% | 6 | 0 | 0 | 0 | 3 | 2 | 3 | |
| British Gas | 65% | 5 | 3 | -3 | 1 | 3 | 2 | 2 | |
| EDF Energy | 65% | 5 | 3 | -2 | 0 | 3 | 2 | 2 |
Based on information provided to us by suppliers in August 2024, and their published fuel mix as we went to press.
*Octopus Energy suppliers London Power and Ebivo Living (to September 2024, after which Ebico Living is powered by Rebel Energy).
**E.ON Next supplies Sainsbury's Energy.
***Ovo Energy supplies Boost Power. Boost Power customers cannot access its solar panel offer.
How we scored energy suppliers on sustainability
Generating, buying and selling renewable power is a key part of energy supplier sustainability, and worth half the points in our assessment.
But these aren't the only factors. This year we also looked at companies' greenhouse gas emissions, as well as other criteria, to get a fuller picture of suppliers' overall environmental impact.
We awarded points for:
- Buying and selling renewable power: Companies were awarded points for buying renewable power directly from generators through PPAs or similar contract arrangements, and additional points if it was from generators that did not receive government subsidies. Companies also gained points for supplying a greater percentage of renewable electricity than the fuel mix average, and for supplying 100% renewable electricity.
- Generating renewable power: Points were awarded to those that generate renewable electricity.
- 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.
- Green gas: We gave a point for selling green gas, and another one if it made up more than 5% of gas sold.
- Time of use (TOU) products and SEG (Smart Export Guarantee) tariffs: Firms received points if they offered one or more TOU products. These encourage customers to use energy at less popular times, which is when the National Grid has most renewable energy in its mix. Suppliers that had above average SEG rates for domestic generators, such as those with solar panels installed, also earned a point.
- Low carbon installations: Suppliers earned points for providing customers with ways to reduce their home's carbon footprint by installing heat pumps, solar panels, battery storage, insulation and EV chargers.
- Greenhouse gas emissions: We looked at companies' scope 1 and 2 (location-based emissions) and whether they were able to provide scope 3 emissions data.
Keen to cut your carbon footprint? Find out more about heating your home with renewable energy or head to our complete energy efficiency guides for more advice.
* Based on an online survey of 3,000 UK adults in August 2024.
