EPC Reform: The New Four-Metric Certificate Explained

As the UK swelters through a record-challenging June heatwave, with the Met Office issuing a rare red extreme heat warning and temperatures pushing 38 to 39°C, the question of how well our homes cope with heat as well as cold has rarely felt more current. That is exactly the gap the reform of Energy Performance Certificates is trying to close.

From one score to four metrics

The reformed domestic EPC replaces the single A to G energy efficiency score with four headline metrics:

• Energy cost — an estimate of what the home costs to run.
• Fabric performance — how well the walls, roof, windows and floors hold heat in (and, increasingly relevant, keep it out).
• Heating system — the efficiency of the installed heating.
• Smart readiness — how well the home can use smart technology to manage energy.

The point is that a single number hid trade-offs. A home could score well on running cost while having poor fabric, or vice versa. Splitting the metrics gives owners, landlords and assessors a clearer picture of where the real weakness is.

The Home Energy Model replaces SAP

Underneath the certificate, the Standard Assessment Procedure (SAP) and its reduced-data version are being replaced by the Home Energy Model (HEM). Following the government's outcome update in March 2026, HEM is now expected in the second half of 2027, with the legacy A to G rating retained alongside it until it is retired around October 2029. EPCs remain valid for 10 years in England, though Scotland is reducing validity to five years.

What it means for assessors and installers

For energy assessors, the move to HEM is a genuine retraining event, not a tweak. For heating and retrofit installers, the separated heating-system and fabric metrics make the case for fabric-first work and low-carbon heat more visible on the certificate itself. It connects directly to the wider direction of travel covered in our guides to EPC C by 2030 for private rentals and the Future Homes Standard.

For the detail of what the new certificate measures, see the government's reforms to the Energy Performance of Buildings regime.

Published 2026-06-24. This article is for general guidance only and does not constitute legal or professional advice. Always refer to the relevant standards and consult qualified professionals for definitive requirements.