How is the ZEB inputted to an EPC?

The ZEB is currently recognised in the Standard Assessment Procedure (SAP) as an electric dry core storage boiler, with 100% efficiency when installed in a heated space. However, this category is based on legacy technology from the 1970s, so EPC scores do not yet capture the full benefits of the ZEB.

Because EPCs are calculated using running costs rather than actual system efficiency, and rely on outdated energy price assumptions, electric heating systems like the ZEB typically receive a lower EPC rating than gas boilers, despite being highly efficient and low carbon.

We are actively working to update how the ZEB is recognised in SAP, with the goal of improving its impact on EPC scores. Our aim is for the ZEB to be included in Appendix Q so that EPC assessors can more accurately account for its performance and benefits.

We expect these changes to come through by the end of the year, although this is subject to regulatory timelines. In the meantime, homeowners can use our cost and carbon calculator for a more accurate view of likely running costs and emissions.