The Department for Energy Security and Net Zero has delayed the launch of the Home Energy Model (HEM), the replacement for the Standard Assessment Procedure (SAP), so that it will no longer go live at the same time as the Future Homes Standard (FHS). The decision was set out in an update dated 10 February 2026 on the consultation outcome page for the Home Energy Model, which was first published on 13 December 2023 and last updated on 2 October 20251.
The department said the delay followed the final stages of internal assurance. The wider FHS package remains on track for Q1 2026, so SAP 10.3 will initially be the sole approved methodology, with HEM expected to follow after at least a three-month delay1.
"In the final stages of internal assurance we have decided to delay the launch of the Home Energy Model ( HEM ) to ensure that when it does go live, it is as robust as possible and delivered to the highest possible standard. This means that HEM will no longer launch at the same time as the Future Homes Standard ( FHS )."
To manage the changeover, both HEM and a version of SAP will be available for a limited period. The department said this dual running allows industry and stakeholders time to adapt, ensures continuity, and enables further validation of the new model before it becomes the sole methodology1.
The consultation on the model, which ran from 10am on 13 December 2023 to 11:59pm on 27 March 2024 after the closing date was extended from 6 March, received 120 responses from organisations, trade bodies, industry professionals, academics and members of the public1. The government response and summary of responses were published on 2 October 20251.
| Item | Detail |
|---|---|
| HEM launch | Delayed; no longer coincides with the FHS |
| FHS package | Remains on track for Q1 2026 |
| Methodology at FHS launch | SAP 10.3 as sole approved methodology |
| HEM timing | Expected after at least a three-month delay |
| Transition | HEM and a version of SAP available for a limited period |
| ECaaS platform | Cloud-based tool available by autumn 2026 |
The HEM engine will continue to be developed through the Energy Calculation as a Service (ECaaS) platform, described as a fast, cloud-based tool available by autumn 2026 to support regulation and third-party applications. Updated technical documentation and validation reports will accompany the next release1. In 2026, the department said it will explore integrating HEM into Energy Performance Certificates (EPCs), aiming to improve clarity and usefulness for households and industry1.
Why it matters for households
SAP is the methodology government uses to estimate the energy performance of homes across the United Kingdom, and it underpins the energy ratings that appear on EPCs1. Because SAP 10.3 will be the sole approved methodology when the FHS package arrives, assessments of new homes in that first period will rest on the existing procedure rather than the new model. The Future Homes Standard sets the compliance route for new build homes, and the department said HEM together with FHS reforms will provide a new methodology for demonstrating compliance1. For a household, the practical effect is that the rating attached to a home at the point of the changeover, and the assumptions behind it, will come from SAP until HEM follows. The dual running period means both methods will be in use for a time, which the department says gives industry time to adapt and allows further validation of the new model1. How the delay affects the treatment of heating systems in new build assessments has not been reported.
What happens next
The FHS package remains on track for Q1 2026, with SAP 10.3 as the sole approved methodology at that point. HEM is expected to follow after at least a three-month delay. The ECaaS platform is due to be available by autumn 2026, and the department said it will explore integrating HEM into EPCs in 20261.