100Green

📅 Last updated: July 2026

About 100Green

100Green was founded in 2001 by Doug Stewart and remains an independent UK energy supplier, based in Ware, Hertfordshire. It was the first UK supplier to offer a choice of green-only tariffs, and the first to launch a tariff that used a smart meter to charge different rates depending on the time of day. It changed its name from Green Energy UK to 100Green to more clearly reflect what it does.

Its defining feature is that it is the only UK supplier to provide 100% green gas alongside 100% renewable electricity. Its electricity comes from a range of British renewable sources, including wind, solar, hydro and biomass, while its green gas is produced through anaerobic digestion of waste. 100Green buys enough renewable electricity to match what its customers use.

100Green is also notable for offering its customers free shares in the business, which entitles them to attend its AGM and question board members, giving customers a genuine say in how the company is run.

It has earned strong recognition. It was named Best Small Supplier in the 2025 Uswitch Energy Awards, and is both a Which? Recommended Provider and a Which? Eco Provider for 2026.

100Green supports traditional prepayment meters, with top-ups available at PayPoint, Payzone and Post Office outlets, and offers a mobile app for managing your account.

100Green tariffs

Every 100Green tariff is 100% green, and none of them carry exit fees, so you are free to switch whenever you like. Here is a summary of the main tariffs.

A standard variable tariff is also available, with 30 days’ notice given before any price change. From July 2026, customers can choose their level of green gas, from at least 10% up to 100%.

Smart meters are available free of charge, arranged by phone or email, and 100Green pays customers who generate their own electricity for any surplus they export to the grid.

100Green and the price cap

One key point to understand is that 100Green has a permanent exemption from the Ofgem energy price cap. This was granted because of how far it goes in generating and supplying renewable energy.

In practice, it means 100Green can charge more than the capped unit rate on its variable tariff, provided customers have actively chosen it. It is worth weighing this up against its green credentials when you compare, so you understand exactly what you are paying for.

100Green customer reviews

100Green scores 4.6 out of 5 on Trustpilot, based on over 1,500 reviews, which places it in the Excellent category. Note that many older reviews were left when the supplier was known as Green Energy UK.

100Green performs strongly on customer satisfaction. In the most recent Which? customer survey, it ranked first out of 17 energy suppliers, with the highest customer score and a four-star rating for overall customer service. For balance, Which? did note weaker results in its switching assessment, and 100Green has recently signed up to Energy UK’s Vulnerability Commitment, which supports customers who are struggling. As a smaller supplier, some customers also reported short-notice price changes.

Expert view

Is 100Green right for you?

100Green may suit you if genuine green credentials matter more to you than the lowest possible price. Its unique 100% green gas, 100% renewable electricity, no exit fees on any tariff and strong customer service record make it stand out, particularly for households that want their gas as well as their electricity to be as green as possible.

The main consideration is cost. Because 100Green is exempt from the price cap, its rates can be higher than capped suppliers, so it is worth comparing to understand the difference. As always, check the tariff against your usage before you decide.

Reviewed by our expert
Jim Pollard
Jim Pollard is Simply Switch’s energy and broadband specialist, helping consumers navigate the ever-changing utilities market with clear, practical advice. With a strong understanding of household bills, tariffs and switching opportunities, Jim focuses on helping people reduce costs, find better-value deals and make informed decisions around their energy and broadband services. His insight into switching trends and household utilities helps consumers make smarter choices with confidence and provides actionable insights that make managing everyday expenses simpler and more cost-effective.