How to Choose a Green Energy Supplier in the UK
Understand renewable sourcing, REGO certificates and the questions to ask when choosing a UK green energy supplier.
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]
Use our referral link, and we'll both get £50 credit once your switch is complete.
Existing customer? Find out how you can benefit too. T&Cs apply (only one switching offer per household)
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.
Octopus Energy is the best all-round green supplier for most households, while 100Green is the only choice for homes that want 100% green gas.
For the average home, Octopus Energy offers the most compelling package. It supplies 100% zero-carbon electricity, drives massive investment in green technology, and keeps its prices at or below the Ofgem price cap. Its smart tariffs also make it the obvious choice if you own an electric vehicle, solar panels, or a heat pump.
However, if you want to completely remove fossil gas from your home without changing your boiler, 100Green is the only supplier offering 100% genuine biomethane. If you are willing to pay a slight premium to directly fund new wind farms, Ecotricity and Good Energy remain the deepest green options on the market.
Frequently asked questions
Does a green tariff mean wind power comes straight to my house?
No. All electricity mixes together in the National Grid, so the physical electricity entering your home is exactly the same as your neighbour's. A green tariff simply means your supplier buys enough renewable electricity (or green certificates) to match the exact amount of power you use.
Is green energy always more expensive?
Not anymore. While some premium suppliers that build their own wind farms charge more, many standard 100% renewable electricity tariffs are currently priced below the standard Ofgem price cap. You can usually switch to a green electricity tariff without increasing your bills.
What is the difference between green gas and carbon-offset gas?
Green gas (biomethane) is made from organic waste and pumped directly into the grid, replacing fossil fuels. Carbon-offset gas is standard fossil-fuel natural gas, but the supplier pays for environmental projects like tree planting to balance out the emissions. Regulators are now heavily restricting the use of offsets to make 'climate neutral' claims.
What happens to my OVO Energy account when E.ON buys them?
E.ON announced its plans to buy OVO in May 2026, but large takeovers take time to complete. For now, nothing changes. Your tariff, prices, and account details will stay exactly the same until the companies officially merge and contact you with the next steps.
Related reviews and comparisons
Octopus Energy vs Ecotricity
Ecotricity may still appeal to households who put its green approach first. Under its 'Bills into Mills' approach, the company says it uses customers' bill money to build new sources of renewable energy. Choosing it is therefore a decision about what your money supports rather than a way to save. On
Read comparison →
Good Energy Review
Good Energy describes itself as one of the UK's first renewable energy companies, with more than 25 years in the business. The brand is a trading name of Good Energy Services Limited, a company registered in England and Wales with its registered office at Monkton Park in Chippenham, Wiltshire.
Read review →
Octopus Energy Review
Octopus Energy was founded by Greg Jackson and is the household energy brand of Octopus Energy Group. In June 2025 the group described itself as a global clean energy technology business working in 32 countries. At that time it supplied more than 9 million households worldwide under the Octopus bran
Read review →
100Green Review
100Green is the trading name of Green Energy (UK) Ltd, a company registered in England with its registered office in Ware, Hertfordshire. It was formerly known as Green Energy UK. It focuses on renewably sourced energy from the UK only, which means no nuclear power. It is a small supplier: in its 20
Read review →
Cheapest Energy Suppliers in the UK
The lowest annual estimate comes with an exit fee, while the cheapest fee-free alternative costs about £33 more a year. We have ranked 60 tariffs this month, and the cheapest deals are a mix of tracker and standard variable tariffs. Tracker tariffs link their unit rates to an outside benchmark, such
Read article →Related guides
How to get a free Octopus Energy cuddly toy?
If you are an Octopus Energy customer, you might recognise their pink, eight-legged mascot, Constantine. Fluffy plush versions of the mascot have become highly popular, often appearing across social media and in homes around the UK.
Read guide →
Octopus Energy Refer a Friend Code – 2026
Octopus Energy runs one of the most popular refer-a-friend schemes in the UK energy market. While many suppliers stopped offering sign-up bonuses during the recent energy crisis, Octopus kept its scheme open. If you use a referral link from an existing customer to switch your gas or electricity, you
Read guide →
Which energy suppliers are going bust?
The UK energy market has seen massive upheaval over the past few years. During the peak of the energy crisis in 2021 and 2022, wholesale costs soared and caused dozens of suppliers to collapse. By July 2026, the market has largely stabilised. However, smaller companies still occasionally fail, and t
Read guide →
Written by
Rob Gibbs
Hi, I'm Rob, and I run Energy-Review.co.uk. I initially started this project in 2018 when I was looking to switch energy suppliers and found there wasn't a website that provided simple, data-backed reviews on all the suppliers available. Since then, I have spent a lot of time (too much, some may say!) looking at all publicly available data about each supplier and writing reviews using this information. These reviews are updated as regularly as possible, and any data is backed up by a source where necessary. I have also started writing guides on various energy-related topics, which hopefully you will find useful. If you find any issues, please use our contact form to let us know.