Standard Assessment Procedure
Source: gov.uk (2025-05-14)

Overview of how a home's energy performance is calculated using the Standard Assessment Procedure (SAP).

Update: 14 May 2025

A version of SAP will be made available alongside the new Home Energy Model software when the Future Homes Standard regulations are laid before Parliament.

This will enable both systems to run on an interim basis, giving the house-building sector time to transition towards working solely with the Home Energy Model in future.

Overview

The Standard Assessment Procedure (SAP) for the energy rating of dwellings (https://bregroup.com/sap/) is the methodology currently used by the government to estimate the energy performance of homes. The methodology has 2 main uses:
- to demonstrate compliance of new homes with Part L of the Building Regulations (https://www.gov.uk/government/publications/methodologies-for-calculating-the-energy-performance-of-new-buildings-in-england-notice-of-approval/notice-of-approval-of-the-methodologies-of-calculation-of-the-energy-performance-of-new-buildings-to-demonstrate-compliance-with-the-building-regulati)
- to generate Energy Performance Certificates (EPCs) (https://www.gov.uk/government/publications/methodologies-for-expressing-the-energy-performance-of-buildings-in-england-and-wales-notice-of-approval/notice-of-approval-of-the-methodologies-for-expressing-the-energy-performance-of-buildings-in-england-and-wales) for all homes, which advise occupants, prospective buyers, landlords, and renters of the energy performance of a property
Non-domestic buildings use a different methodology, called the Simplified Building Energy Model (SBEM) (https://www.uk-ncm.org.uk/index.jsp).

SAP plays a key role in developing, implementing, and monitoring government policies on energy efficiency, fuel poverty and heat decarbonisation, and is used across the whole building industry.

The history of SAP

SAP was developed by the Building Research Establishment (BRE) for the former Department of the Environment and was based on the BRE Domestic Energy Model (BREDEM) (https://files.bregroup.com/bre-co-uk-file-library-copy/filelibrary/bredem/BREDEM-2012-specification.pdf). SAP was first published in 1993 and has since been updated periodically, in 1998, 2001, 2005, 2009, 2012, and most recently in 2022.

In 1994, SAP was first cited in the Building Regulations as the means of assessing the energy performance of dwellings. In 2007 it was adopted as the methodology behind Energy Performance Certificates (EPCs).

Reduced data SAP (RdSAP) was introduced in 2005 as a simpler and lower cost method for assessing existing dwellings. An RdSAP assessment will use a set of assumptions about the dwelling, reducing the volume of data an energy assessor must collect.

Current methodologies

The current version of SAP is SAP 10.2 (https://bregroup.com/expertise/energy/sap/sap10).

The current version of RdSAP is RdSAP 10 (https://bregroup.com/expertise/energy/sap/sap10).

You can find detail of the changes in the RdSAP 10 specification (https://files.bregroup.com/SAP/RdSAP10-dt13.02.2024.pdf).

You can find more information on SAP and RdSAP on the Building Research Establishment’s (BRE) (https://bregroup.com/sap/sap10/) site.

The future of SAP

Following recommendations by the Climate Change Committee (CCC) (https://www.theccc.org.uk/publication/uk-housing-fit-for-the-future/), the government is developing a new methodology to increase its accuracy, robustness, and ensure it is fit for net zero.

The Home Energy Model

The Home Energy Model will replace the SAP for the energy rating of dwellings. It is still under development and we will implement the first version alongside the Future Homes Standard in 2025.

Consultations:
- Home Energy Model consultation (https://www.gov.uk/government/consultations/home-energy-model-replacement-for-the-standard-assessment-procedure-sap) (13 December 2023 to 27 March 2024)
- Future Homes Standard assessment consultation (https://www.gov.uk/government/consultations/home-energy-model-future-homes-standard-assessment) (13 December 2023 to 27 March 2024)
- Future Homes and Buildings Standards consultation (https://www.gov.uk/government/consultations/the-future-homes-and-buildings-standards-2023-consultation) (13 November 2023 to 27 March 2024)
Technical documents:
- Home Energy Model: technical documentation (https://www.gov.uk/government/publications/home-energy-model-technical-documentation)
- Home Energy Model: validation documentation (https://www.gov.uk/government/publications/home-energy-model-validation-documentation)
- Home Energy Model: Future Homes Standard assessment: technical documentation (https://www.gov.uk/government/publications/home-energy-model-future-homes-standard-assessment-technical-documentation)
- Home Energy Model reference code (https://dev.azure.com/Sustenic/Home%20Energy%20Model%20Reference)
Scoping study:
- The future of SAP calculations (https://etude.co.uk/how-we-work/the-future-of-sap-calculations/)