Energy suppliers selling ‘100% renewable’ tariffs can deliver very different amounts of renewable electricity when customers actually use it, with matching scores ranging from 87% to just 2%.
According to the data published by comparison specialist Matched, no tariff sold as “100% renewable” delivers renewable power in every hour its customers use it. The Matched Clean Power Index ranks 28 suppliers from April 2025 to March 2026 – using data comparison between demand and generation within the same half-hour. This differs from current renewable claims, which use records of the past 12 months of what a supplier has bought, but do not record hourly usage.
Overall, the findings highlight a problem with the way renewable electricity is currently measured; suppliers can market tariffs as ‘100% renewable’ using Renewable Energy Guarantees of Origin (REGOs), which don’t represent hourly useage, and therefore don’t show the true balance of renewable vs fossil fuels.
Matched says the issue is becoming more important as the UK relies increasingly on wind and solar power. Renewables are volatile, meaning if consumers can see when renewable electricity is available, they can leverage this into cleaner periods by charging electric cars or running heavy appliances.
Joe Kwiatkowski, founder of Matched, says: “If you turned the heating on at 6 pm on a January weekday, most of your ‘100% renewable’ supply was not matched by renewable generation at all. Your supplier is following the rules. The problem is that the rules let the label say something the product does not deliver. Renewable claims should be measured in the hours the power is used. Consumers would then see the difference between suppliers, and the premium they pay for a green tariff would go towards renewable power, storage and flexibility for the hours that need it. The suppliers at the top of the Index show this is possible now.”
Matched is calling on Ofgem to require hourly evidence behind renewable tariff claims. The organisation says the data already exists and changes to the rules would give consumers greater transparency over what their renewable tariffs actually deliver.
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