From July 2026, customers of the supplier 100Green will be able to choose between at least 10% green gas and 100% green gas, according to Which?1. The consumer body reports the change in its review of the company, published on 16 June 2026, which also names 100Green a Which? Eco Provider for energy in 2026 and a Which? Recommended Provider for the second year in a row1.
Which? describes 100Green as "a small but long-established energy supplier and the only one to sell 100% green gas"1. The company, formerly known as GEUK, was established in 2001, making it one of the oldest energy firms outside the traditional big firms1. Which? states that 100Green buys enough renewable electricity directly from generators to match what its customers use, including solar, wind, biomass and hydro, and that it is the only firm from which both 100% renewable electricity and 100% green gas can be bought1. It also sells three multi-rate tariffs designed for different lifestyles, and Which? says it is the only supplier with a tariff that protects wildlife by avoiding electricity generated where there are migrating birds and fish or fragile ecosystems1. The sustainability assessment, based on information supplied by companies in March 2026, gave 100Green a score of 70%, against a range across suppliers of 0% to 85%1.
In the annual Which? customer survey, 100Green was ranked first out of 17 energy companies, rated by 11,945 members of the public1. Its customer score was 82%, with four stars for overall customer service and three stars in the remaining categories, including ease of contact, customer communications and value for money1. No provider achieved more than three stars for value for money1. The customer survey was based on a survey of 146 100Green customers carried out in September-October 20251.
Which? combines that survey with an assessment of suppliers' practices and policies. 100Green's total score was 72%, made up of a customer survey score of 82% and a Which? assessment score of 61%1. The assessment, carried out in September-November 2025, scored the company as follows1:
| Assessment area | Score |
|---|---|
| Complaints (out of 15) | 12 |
| Contacting your supplier (out of 12) | 9 |
| Help for those who need it (out of 10) | 4 |
| Smart meters (out of 10) | 6 |
| Switching (out of 5) | 1 |
Which? reports that 19% of the 100Green customers in its survey said they made a formal complaint in the last year, which it describes as above average when compared with other providers in the survey1. The most common issues experienced over the last year were short-notice price increases (19%), needing a new energy meter installed (17%), and smart meters not sending readings automatically (15%)1. The company received high marks for its handling of complaints and for the methods of contact it provides, offering 12 hours daily on its phone line on weekdays and a few hours on both weekend days, with equally extensive email monitoring hours and support through live chat and social media1. It scored four out of a possible ten for providing help for those who need it; at the time of the assessment it was not a signatory of EnergyUK's voluntary Vulnerability Commitment, and Which? states it has since signed up1. It scored one out of a possible five for its switching practices1. Which? also states that 100Green supports traditional prepayment meters, where customers top up a key or card at Paypoint, Payzone or Post Office outlets1.
"From July 2026, customers can choose between at least 10% green gas and 100% green gas."
Why it matters for households
Green gas is not the same product as renewable electricity. A household choosing a 100% green gas option is buying a supply whose gas content is matched by green sources, rather than the minimum proportion. The choice reported here means a household on 100Green's gas supply will be able to decide how much of that supply is green gas, with at least 10% as the lower option and 100% as the upper one1. Which? does not report the price difference between the two levels, so the cost of choosing the higher proportion has not been reported1.
For a home's energy independence, the relevant point is what the supplier sources directly. Which? states that 100Green buys enough renewable electricity directly from generators to match what its customers use1. That is a matching arrangement rather than a claim about where the physical electrons or gas molecules come from, and Which? does not describe the origin of the green gas itself1.
The wider picture from the same review is that customer satisfaction and behind-the-scenes practice do not move together. 100Green ranked first of 17 companies on customer score, yet scored 61% in the assessment of practices, with its weakest marks on help for those who need it and on switching1. Households weighing a green gas option against the practicalities of switching, metering and support may find those two sets of figures point in different directions.
What happens next
The choice of green gas levels applies from July 20261. Which? reports that 100Green has signed up to EnergyUK's voluntary Vulnerability Commitment since the assessment period1. No date has been reported for that change.
Sources1 cited
- 100Green review - Which?, which.co.uk