Home Energy Model Replacing SAP in 2025

What is the Home Energy Model?

The Home Energy Model (HEM) is a new government calculation methodology designed to assess the energy performance of homes across the United Kingdom. It is set to replace the current Standard Assessment Procedure (SAP) methodology in 2025.

When was the home energy model announced?

The Home Energy Model was announced by the UK government in December 2023. This announcement was part of three consultations focused on the Home Energy Model and the Future Homes and Buildings Standards. Specifically, two consultations were released regarding the Home Energy Model:

1. "Home Energy Model: Replacement for the Standard Assessment Procedure (SAP)" - This consultation covered the methodology that will replace SAP for assessing the energy performance of homes.

2. "Home Energy Model: Future Homes Standard Assessment" - This consultation addressed the methodology that will be used to demonstrate compliance of new dwellings with the Future Homes Standard.

   
   

These consultations were initially set to close on March 6, 2024, but the deadline was extended to March 27, 2024. The extension was due to an issue with the consultation version of the Home Energy Model. The announcement of the Home Energy Model represents a significant shift in how the UK government plans to assess and regulate energy performance in homes, with the new model set to replace the current Standard Assessment Procedure (SAP) methodology.

Why is home energy model replacing SAP?

The Home Energy Model (HEM) is replacing the Standard Assessment Procedure (SAP) for several key reasons:

1. Improved accuracy and detail:

2. HEM uses a 30-minute time resolution simulation, compared to SAP's monthly calculations, allowing for more precise energy use predictions.

3. It requires more specific information about dwellings, including number of bedrooms, appliance ratings, and precise measurements of living spaces.

4. Outdated methodology:

5. SAP was first introduced in 1993 and last updated in 2012, making it outdated for modelling modern domestic energy use.

6. Climate experts and property industry professionals have recommended that SAP is no longer fit for purpose, especially for driving the property sector towards decarbonisation.

7. Enhanced capabilities:

8. HEM can model energy flexibility and smart technologies due to its half-hourly simulation capability.

9. It considers potential future technologies like heat batteries, offering a more holistic and future-proof assessment.

10. Transparency and flexibility:

11. HEM will be open-source, with the codebase published to increase transparency.

12. It's built on a modular framework, allowing for greater flexibility and continuous improvement.

13. Alignment with current goals:

14. HEM is designed to better align with current technological advancements and political conditions in the UK, particularly in supporting the transition to net-zero emissions.

15. Improved consistency:

16. The centralized, open-source nature of HEM aims to reduce inconsistencies that arose from different interpretations and implementations of SAP by various parties.

    
    

By replacing SAP with the Home Energy Model, the UK government aims to create a more robust, accurate, and future-proof system for assessing home energy performance, which is crucial for meeting climate goals and improving energy efficiency in the housing sector.

How will the Home Energy Model differ from SAP?

The Home Energy Model (HEM) will differ from the Standard Assessment Procedure (SAP) in several key ways:

Improved Accuracy and Detail

• HEM uses a 30-minute time resolution simulation, compared to SAP's monthly calculations, allowing for more precise energy use predictions.

• It requires more specific information about dwellings, including number of bedrooms, appliance ratings, and precise measurements of living spaces.

• HEM incorporates local weather data for improved climate impact predictions.

  
  

Enhanced Capabilities

• Able to model energy flexibility and smart technologies due to its half-hourly simulation capability.

• Considers potential future technologies like heat batteries, offering a more holistic and future-proof assessment.

• Allows division of buildings into thermal zones for more accurate heat loss calculations.

  
  

Transparency and Flexibility

• HEM will be open-source, with the codebase published to increase transparency.

• Built on a modular framework, allowing for greater flexibility and continuous improvement.

  
  

Updated Assumptions

• HEM includes updated standardized assumptions, such as:

  • Occupancy based on both total floor area and number of bedrooms.

  • Reduced assumed energy demand for household appliances by about 25% to reflect improved efficiency.

  • More accurate modelling of cooking appliances based on actual fuel types used.

    
    

Methodology Structure

• HEM uses "wrappers" to distinguish different use cases, allowing for more flexibility in updates and applications.

• It's built on international standards and has a modular architecture for easier updates and maintenance.

  
  

These changes aim to make HEM more robust, accurate, and fit-for-purpose in supporting the transition to net-zero emissions compared to the current SAP methodology.

How will Home Energy Model impact EPCs?

The Home Energy Model project will not change the Energy Performance Certificate (EPC) itself. However, the government is working on proposals to improve aspects and areas relating to EPCs, such as the performance metrics that they display.

When will Home Energy Model be implemented?

The implementation timeline for the Home Energy Model (HEM) is as follows:

1. The first 'live' version of the Home Energy Model is planned to be implemented alongside the Future Homes Standard in 2025.

2. Key steps leading up to the implementation include:

   • The government aims to publish responses to the Home Energy Model Future Homes Standard (FHS) assessment wrapper consultations in 2024.

   • Consultation on the EPC wrapper methodology is planned for 2024.

   • Further development of features, including all technologies currently in SAP 10.2 and existing Appendix Q technologies.

   • Rebuilding of the Product Characteristics Database (PCDB).

3. The rollout of the Future Homes Standard, which will include the use of the Home Energy Model for new buildings only, will commence in 2025.

4. After the initial implementation for new buildings, the Home Energy Model will be expanded to include the production of Energy Performance Certificates (EPCs) for existing homes.

   
   

It's important to note that while 2025 is the target date for implementation, the Home Energy Model is still under development, and the government is working through consultation responses and further refinements before the final rollout.