Exactly. That’s the core problem the Index exposes. Under current UK rules (and indeed in most countries), suppliers can legally call their power “100% renewable” even when it’s mostly gas at times of low renewable generation. They can do this by offsetting the non-renewable deficit with certificates from sunny summer hours.

What we've tried to do at Matched is make this fact visible, showing which suppliers actually deliver clean power hour by hour rather than just on paper. A number of suppliers (notably Good Energy and Octopus) perform surprisingly well, be procuring renewable power that aligns well with their consumer's demand.