Matched publishes the second Clean Power Index today. It ranks 28 suppliers on how much renewable electricity they supply in the hours their customers actually use it, across the whole year.
Among the household suppliers that sell a renewable tariff, the share of their customers’ use matched by renewable generation in the same half-hour runs from 87% down to 2%. No tariff sold as “100% renewable” delivers renewable power in every hour its customers use it.
A customer who turns the heating on at 6 pm on a January weekday is very likely to be powered by gas. The bill does not say so, and neither does the tariff page or the comparison site. This isn’t illegal: the suppliers are following the rules as they are written by Ofgem.
The same label over different products
The Index covers 28 suppliers for April 2025 to March 2026, of which 14 sell to households and ten of those sell a renewable tariff.
Good Energy leads on 87% renewable matched, then Octopus 67%, Ecotricity 67%, 100 Green 61%, So Energy 59%, British Gas 42%, EDF 19%, E.ON Next 15%, ScottishPower 14% and OVO 2%.
The other four household suppliers, Fuse Energy, Utility Warehouse, Utilita and Outfox The Market, make no renewable claim and redeemed no renewable certificates, so they score 0%.
Even the best supplier leaves 13% of what its customers used covered by non-renewable sources, and at the bottom of the table almost all of the supply is non-renewable. What separates them is what they buy.
A supplier can buy renewable power for the hours its customers use it, or it can buy certificates from hours of surplus output, often summer solar, and set them against winter evenings it supplies from elsewhere. Today’s Ofgem rules let both describe the result the same way.
How the Index measures it
Renewable claims currently rest on annual certificate totals, which record what a supplier bought over twelve months but say nothing about the hour the power was used.
The Clean Power Index compares demand and generation within the same half-hour instead, using public data from Elexon for demand, NESO for generation and Ofgem for REGO certificates.
The methodology is published in full at matched. Energy/methodology. It has been reviewed by more than 30 experts across the sector, including researchers at the University of Oxford and Imperial College London and several energy suppliers.
Uswitch now uses the Index to rank energy tariffs.
Without this kind of measurement, consumers have no way to tell the two products apart.
What needs to change
Ofgem rules treat all of these tariffs as one product. A supplier that buys renewable power for the hours its customers use it may claim no more than a supplier that buys certificates once a year, and the customer paying the premium has no way to tell which one they have bought.
Wind and solar arrive when the weather delivers them, so electricity is no longer the constant, uniform product the rules were written for. Some hours are clean and cheap, and some hours run on gas and cost more.
A household that can see the difference can act on it, charging the car, warming the house and running the heavy appliances in the clean hours, and using less in the evening peak. Demand that can move is what the system needs next, because it is what makes storage and flexibility pay.
None of that works with the current opaque claims of ‘100% renewable tariffs’. Measuring the claim in the hours the power is used would give the customer a number to check, and would give the suppliers that already match demand something to show for it.
Matched is asking Ofgem to require hourly evidence behind renewable tariff claims. The data exists; we just need an update to the rules to give consumers the transparency they deserve.
Joe Kwiatkowski, founder of Matched, said, “If you turned the heating on at 6pm 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.”
Fran Woodward, Managing Director of Supply for Good Energy, commented, “At Good Energy, we’ve long believed that consumers deserve greater transparency about where their electricity comes from and how renewable claims are being made. That’s why we believe hourly matching is the future. It shows how much clean power is being delivered when customers actually need it.”
