DESNZ release Home Energy Model Consultation Response
Today (2nd October 2025), the Department for Energy Security and Net Zero (DESNZ) have published the response to the consultation, officially titled ‘Home Energy Model: replacement for the Standard Assessment Procedure (SAP)’. Elmhurst take a look at the key outcomes of their response.
What did the consultation cover?
The Home Energy Model consultation ran between December 2023 and March 2024 and posed questions relating to the replacement of Standard Assessment Procedure (SAP) with the new Home Energy Model (HEM). Key areas covered were:
- Summary of the development and validation work undertaken to date
- Invitation of feedback to enable further model development in advance of its introduction
Elmhurst responded to this consultation on behalf of our members and you can read our full consultation response here >
The Government Response
The key areas of the Home Energy Model consultation and responses include:
A new delivery model
As expected HEM will be delivered to the industry differently to SAP. The HEM is published in open source environment which should encourage peer review and transparency of the model. Wrappers will need to be used to utilise the core HEM model for a specific purpose, for example EPCs.
The consultation confirmed that core HEM will be facilitated through Energy Calculation as Service (Ecaas) and this will only be accessible to energy assessor accreditation schemes. Schemes will then be responsible for developing their own HEM application to connect to the service and allow energy assessors to use software – Elmhurst has already been developing our future HEM application on this basis.
Interestingly, there was also the mention of fees to use and maintain ECAAS which is something Elmhurst have been asking for clarity on for some time. MHCLG will continue to discuss this area with schemes.
New calculation methodologies
HEM is based on new modern international standards for energy modelling, specifically BS EN ISO 52016-1:2017 which is different to SAP. Government confirmed they will increase the time resolution of the model compared to SAP. Where SAP currently works on a monthly basis, HEM can use more detailed timesteps, expected to be half hourly. This allows more accurate modelling of technologies that will be key for the future such as heat pumps, heat batteries, electric batteries, smart tariffs and load shifting appliances. Finally, there was confirmation that the calculation of infiltration and ventilation will now be based on BS EN 16798-7:2017 replacing the previous approach.
Validation of HEM
The Government has reaffirmed its commitment to ensuring the Home Energy Model (HEM) is rigorously validated through ongoing testing, inter-model comparisons, and real-world case studies. While recognising concerns around SAP comparisons and testing methods, it stresses that validation is an ongoing process, with continuous improvements and stakeholder engagement central to building confidence in the model’s reliability and accuracy.
You can read the full Government response here >
Elmhurst Thoughts
Elmhurst New Build Dwellings Manager Jason Hewins commented;
“We are pleased to see the Home Energy Model consultation responses published by DESNZ. This gives clarity in some areas of methodology.
We are now awaiting the consultation responses for the Future Homes Standard and the use of the Home Energy Model for the Future Homes Standard which are expected before the end of the year.”
Further Information
View the Home Energy Model Consultation – https://www.gov.uk/government/consultations/home-energy-model-replacement-for-the-standard-assessment-procedure-sap
Elmhurst Response – https://www.elmhurstenergy.co.uk/app/uploads/2024/03/Consultation-Response-HEM-for-SAP-002-1.pdf
Government Response –https://assets.publishing.service.gov.uk/media/68dd03238c1db6022d0c9f82/home-energy-model-government-response.pdf