The methodology that underpins the Energy Performance Certificate system is undergoing a major overhaul in the middle of June 2025.
The changes are the most significant in over a decade and are expected to improve the accuracy of EPCs, especially for flats and mid-terrace homes.
The new EPCs should also better reflect how homes are used, and help inform decisions on energy efficiency.
The changes come from something called the Reduced Data Standard Assessment Procedure (RdSAP). It uses assumptions about how buildings are constructed and occupied to generate a rating of a property’s energy efficiency.
Propertymark – which has made a detailed study of the changes – says energy assessors will now collect and record more specific information about a property, including types of glazing and their condition, heating system efficiency based on evidence such as model numbers or manufacturer data, and the presence of smart heating controls.
Home improvements, such as added insulation or new windows, will only be reflected if evidence is available.
This means EPCs will now depend much more heavily on the documentation that homeowners, landlords, and agents can provide.
Previously, if a heating system’s details couldn’t be verified, default assumptions were used: these are now believed to have underestimated a property’s ene eggy efficiency.
However under RdSAP if no documentation can be provided, the system’s efficiency may be rated lower, potentially impacting the EPC score.
The update includes refined methods for calculating floor area and insulation levels, providing a more precise understanding of a home’s heat retention and energy use.
And RdSAP adjusts how heat loss is calculated for flats and terraced homes, which were previously disadvantaged by default assumptions. This could lead to improved EPC ratings for these types of properties.
Propertymark says it welcomes making EPCs “more robust and meaningful.”
But it adds: “We continue to push for clear guidance and support for landlords and agents to navigate upcoming changes, realistic implementation timelines that allow the sector to prepare, and funding to help with the cost of improvements, particularly for small landlords.
“These themes are consistent with our wider work calling for reform of the EPC system, fairer access to retrofit funding, and better communication from governments to landlords and property professionals.”
The trade body says agents should in particular help landlords prepare for the change.
“Going forward, accurate records and receipts will be critical—especially for insulation, heating upgrades and double glazing.
“EPC ratings might initially drop if no evidence is provided, even if improvements have been made, so having a clear paper trail can protect property owners from unnecessary retrofit costs.”
Written by Graham Norwood for Estate Agent Today 31.5.25
