HEM has not replaced SAP yet
The Home Energy Model is intended to become the future methodology for assessing the energy performance of homes. Government guidance updated in June 2026 confirms that HEM did not launch alongside the Future Homes Standard and that SAP 10.3 remains the sole approved methodology at present.
The government intends to introduce HEM alongside SAP 10.3 after assurance and readiness work. Published transition material describes a dual-running period before HEM eventually becomes the sole methodology for new-home compliance.
Why the change is significant
HEM is designed around a more detailed calculation approach than the monthly structure associated with earlier SAP methodology. Its development addresses low-carbon heating, energy flexibility and a wider range of building-performance questions.
That does not mean live projects should switch methodology in anticipation. Assessments must follow the approved route that applies to the project at the relevant time.
What project teams should do now
Keep design information coordinated, retain evidence and identify the project transition date early. As the approval timetable develops, confirm the required methodology and software before relying on preliminary results. We will update this article when an operative HEM route and transition dates are formally confirmed.
Official sources
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