EPCs overestimate actual energy use by up to 344 per cent

Energy Performance Certificates (EPC) have come under fire in new reporting from The Times, which found that the certificates can overestimate actual energy use by up to 344 per cent.

This suggests homeowners and landlords may be wasting money on energy efficiency upgrades that will have a negligible impact on their energy bills and the environment.

Climate fintech company CarbonLaces compared the EPCs of more than 17,000 homes against their actual energy use and found that, on average, they overestimate by a factor of two.

The Times said: “The average metered gas and electricity use for all the properties studied was 125kWh per square metre a year — 91 per cent lower than what their EPCs claim (239kWh/m2/yr).”

The lower the EPC rating, the bigger the overestimation, the Times found. For properties with the lowest rating of G, EPCs say they use 656kWh/m2/yr, despite the smart meters showing they use only 151kWh/m2/yr — a 344 per cent gap.

D-rated homes, the most common in Britain, were found to have a 52 per cent overestimation.

F-rated homes showed a reality gap of 161%, while those rated E and C had a gap of 90% and 23%, respectively. A and B-rated homes reflect the most accurate EPC ratings, but still slightly misrepresent true energy use.

The Times found that EPCs overestimate not only energy use, but also carbon emissions – between 20 per cent in C-rated homes and 308 per cent in G-rated – which the CarbonLaces report described as “creating misleading baselines”.

The Times points out that inaccurate and unreliable EPCs could have widespread consequences. Landlords are already banned from letting properties with F and G ratings, and under government proposals would be prevented from letting any property with less than a C rating from 2025. There are also proposals that mortgage lenders have an average C rating in their portfolio by 2030. Without accurate EPCs these proposals could potentially have a massive effect on the housing market, particularly the already stretched rental sector.