SAP to HEM: The Future of Home Energy Assessment in the UK

The way energy performance is assessed in UK homes is entering a new phase. For many years, the Standard Assessment Procedure (SAP) has provided the framework through which residential developments have demonstrated compliance with Building Regulations and achieved Energy Performance Certificates (EPCs). As the industry moves towards the introduction of the Future Homes Standard, the Home Energy Model (HEM) will become the new basis for assessing residential energy performance, marking an important step forward in how homes are evaluated.

Expected to be introduced during the second half of 2027 alongside the Future Homes Standard, HEM will initially run alongside SAP 10.3 during a transition period before becoming the sole method for demonstrating compliance and producing EPCs. While the change will introduce a new assessment process, it also signals a wider shift towards understanding how homes are expected to perform once people are actually living in them.

At the heart of the transition is a move towards a more representative understanding of how homes are expected to perform once occupied. The current SAP methodology is based on monthly averaged calculations, which have provided a robust and widely used framework for many years. HEM moves towards a dynamic modelling approach, enabling performance to be assessed in a way that more closely reflects the variations experienced throughout the year. This creates an opportunity to better understand how building fabric, energy systems and occupancy patterns interact over time, providing greater insight into the operational performance of a home.

The introduction of HEM comes at a time when building performance is becoming an increasingly important consideration across the residential sector. As developers continue to respond to evolving sustainability expectations, changing regulations and advances in building technology, there is growing interest in ensuring that predicted performance provides a clearer picture of how homes are likely to operate in practice. The additional detail provided through HEM supports this by taking a broader range of factors into account during the assessment process.

A key aspect of HEM is the increased level of detail incorporated into the assessment process. Under SAP, calculations broadly distinguish between the main living area and the remainder of the dwelling. HEM introduces a zonal approach, enabling individual areas of a home to be assessed separately and creating a more detailed understanding of how different spaces perform.

This approach recognises that homes are used in different ways throughout the day and that energy demand, occupancy and environmental conditions can vary significantly between rooms. It also reflects the growing range of systems and technologies now being incorporated into residential developments, helping designers and developers build a more detailed picture of overall building performance.

The level of information entered into HEM will also increase. Heating systems, ventilation strategies and other building services will be assessed through a more detailed process, creating a clearer view of how these elements contribute to the performance of the finished home. As expectations around energy efficiency continue to rise, this additional level of insight will help inform design decisions earlier in the development process.

The introduction of HEM also brings changes to the way assessments are undertaken. Rather than relying on multiple independent calculation engines, HEM is being developed as a centralised, cloud-based platform that software providers can integrate into their own services. This creates a more consistent approach across the industry while providing a platform that can continue to adapt as future requirements emerge.

HEM will also move away from the European standards that have historically informed SAP calculations. This gives the UK an opportunity to develop an approach that reflects the Future Homes Standard and supports the direction of travel for residential development in the years ahead. As energy performance and operational efficiency continue to shape the homes being delivered across the country, the assessment framework will play an increasingly important role in supporting those objectives.

Although implementation remains some way off, the transition is already beginning to influence discussions across the residential sector. Developers, designers and sustainability specialists are starting to consider how the increased level of detail, dynamic modelling approach and revised compliance framework could influence future projects. The dual-running period will provide valuable time for project teams to become familiar with the new system and understand how it will fit within future development programmes.

The move from SAP to HEM is ultimately about building a clearer understanding of how homes perform. As the Future Homes Standard approaches, the industry has an opportunity to embrace a framework that provides greater insight into energy performance, supports informed design decisions and strengthens the connection between compliance modelling and operational outcomes. Developers who begin engaging with the changes now will be well placed to navigate the transition and continue delivering high-quality, energy-efficient homes that meet the expectations of both future regulation and future occupants.

For more information on the transition from SAP to HEM and what it could mean for your developments, please get in touch with Soraya Mohajeri, Theodora Vagiou or any of our MEP Engineering specialists.