The Home Energy Model: What It Means for the Social Housing Sector

By Luke Beard · 13 October 2025

The Department for Energy Security and Net Zero (DESNZ) has confirmed that the Home Energy Model (HEM) will replace the Standard Assessment Procedure (SAP). This marks a significant evolution in how the energy performance of homes is assessed in the UK. HEM will underpin key housing policies including the Future Homes Standard, Energy Performance Certificates (EPCs), and retrofit programmes such as SHDF and ECO.

Why the Change?

SAP has been the industry standard since 1993, but it has increasingly failed to reflect how homes perform in real life. Its use of broad averages and static assumptions often results in energy ratings that don’t match actual performance, particularly in highly efficient homes.

Industry feedback during the consultation (December 2023 to March 2024) reinforced the need for change, with stakeholders broadly welcoming HEM while highlighting concerns about training, accessibility, and the need for clearer retrofit guidance. The consensus was clear: a more accurate, transparent model is essential.

What Makes the Home Energy Model Different?

• Half-hourly time steps – for more accurate simulations of energy use instead of estimating energy use based on monthly averages (like SAP does), the new model looks at how energy is used in a home every 30 minutes. This means it can better reflect how people actually live such as when they turn on heating, cook, or use appliances, and how technologies like heat pumps or solar panels respond throughout the day.
• Modular architecture – that allows the same model to serve multiple policy needs. The core model stays the same, but it can be adapted for different purposes, whether it’s calculating an EPC rating, checking compliance with building regulations, or assessing retrofit plans. This makes it easier for government and industry to use one consistent system across different policies.
• Open-source code – publicly available for transparency and peer review, helping build trust and keeping the model up to date.
• Cloud-based delivery via “Energy Calculation as a Service” (Ecaas) – accessible to accredited schemes. Instead of downloading software, assessors will access the model online through a secure platform. Only approved organisations will be able to use it, which helps maintain quality and consistency. However, this also raises questions about cost and accessibility, especially for smaller providers.