Home Energy Model

The Home Energy Model (HEM) is the UK government's next-generation replacement for the Standard Assessment Procedure (SAP), designed to deliver more accurate, real-world energy assessments for residential buildings. UK Building Compliance is already preparing for this transition — our assessors are registered with Elmhurst Energy and ready to deliver HEM assessments as soon as the new standard is formally introduced under the Future Homes Standard.

What Is the Home Energy Model?

The Home Energy Model (HEM) is the UK government's upcoming replacement for SAP — the current official method used to evaluate the energy efficiency of dwellings. Developed in line with the Future Homes Standard, HEM will deliver significantly more accurate energy assessments that better reflect real-world building performance.

While SAP calculations have served the industry for decades, the methodology has limitations when modelling modern low-carbon homes and technologies such as heat pumps, battery storage, and advanced insulation systems. The Home Energy Model addresses these limitations through a fundamentally different approach to energy modelling.

Key innovations include half-hour energy modelling intervals (compared to SAP's monthly averages), thermal zoning that allows detailed heat loss calculations for each section of the building, integration of local weather data and household appliance ratings, and an enhanced database of building products and technologies. These changes are designed to produce results that much more closely reflect actual energy use in occupied homes.

Why Is the Home Energy Model Important?

The Home Energy Model represents the most significant change to residential energy assessment in the UK for decades. It forms a core part of the government's pathway to net-zero carbon buildings, and understanding its implications is essential for anyone involved in residential construction.

The enhanced accuracy of HEM means that building designs will need to genuinely perform well — not just meet a simplified calculation target. This is good news for occupants (who will benefit from homes that truly deliver low energy bills) and for the environment (as actual carbon emissions will more closely match the assessed performance).

For developers, architects, and housebuilders, the transition to HEM means that design decisions will need to be more carefully considered. The half-hourly modelling approach will highlight issues that SAP's monthly averaging can mask — such as peak heating demand, the interaction between heat pumps and building fabric, and the real contribution of solar PV to meeting heating loads.

When Will the Home Energy Model Be Introduced?

The rollout of the Home Energy Model is expected to align with the introduction of the Future Homes Standard in 2026. Until then, SAP calculations remain the current requirement for compliance with Part L of the Building Regulations.

There is no need to delay your project. SAP assessments are still fully valid and required for all current building regulations submissions. However, forward-thinking developers are already considering how HEM will affect their designs, and UK Building Compliance is incorporating HEM-ready insights into our current evaluations wherever possible.

What's Changing with the Home Energy Model?

• Half-hourly modelling intervals — HEM models energy use in 30-minute time steps rather than monthly averages, providing a much more granular and accurate picture of building performance.
• Thermal zoning — Buildings are divided into thermal zones, allowing detailed heat loss calculations for each section rather than treating the whole dwelling as a single zone.
• Local weather data — HEM integrates location-specific weather data rather than relying on regional averages, improving accuracy for individual sites.
• Enhanced technology modelling — Better representation of modern technologies including heat pumps, battery storage, solar PV, MVHR systems, and smart controls.
• Transparency — The model is being developed as an open-source tool, allowing greater scrutiny and continuous improvement by the industry.
• Appliance energy use — HEM incorporates household appliance energy ratings, providing a more complete picture of total energy consumption.

How Does This Affect Your Project?

Whether you are planning a new build, extension, or conversion, the Home Energy Model will become the standard assessment method for Part L compliance once the Future Homes Standard is introduced. Key implications include:

• Fabric-first design becomes more important — With more accurate modelling, the genuine thermal performance of the building envelope will have a greater impact on assessment results.
• Heat pump performance will be modelled more accurately — Half-hourly modelling better captures the interaction between heat pumps, building fabric, and occupant behaviour.
• Thermal bridging will matter more — With detailed thermal zoning, junction performance will have a more significant impact on results.
• Airtightness standards may increase — More accurate modelling of heat loss through air leakage may drive tighter airtightness targets.
• Ventilation design needs careful consideration — The interaction between airtightness and ventilation will be modelled in greater detail.

Why Choose UK Building Compliance?

UK Building Compliance is at the forefront of the transition from SAP to the Home Energy Model. Our assessors are registered with Elmhurst Energy and hold accreditations with ATTMA, Stroma, ABBE, BPEC, and UKAS. We are actively preparing for HEM, ensuring our team is trained and ready to deliver assessments from day one of the new standard.

In the meantime, we continue to provide fully certified SAP calculations with HEM-ready insights built into our evaluations. This means your current projects are compliant today while being designed with an awareness of future requirements.

We offer transparent pricing, fast turnaround, and guidance tailored to both current and future regulations. Trusted by architects, developers, and housebuilders across the UK, we are your partner for navigating the changing landscape of residential energy assessment. Based in Hinckley, Leicestershire, we provide nationwide coverage. Call 01455 242297 for a free quote.