Overview of how a home's energy performance is calculated using the Standard Assessment Procedure (SAP).
The Standard Assessment Procedure (SAP) for the energy rating of dwellings 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
- to generate Energy Performance Certificates (EPCs) 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).
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). 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.
The current version of SAP is SAP 10.2.
The current version of RdSAP is RdSAP 2012.
The government is currently working on an RdSAP update (RdSAP 10), which will be available for use in early 2024.
You can find detail of the upcoming changes in the RdSAP 10 specification.
You can find more information on SAP and RdSAP on the Building Research Establishment’s (BRE) site.
The future of SAP
Following recommendations by the Climate Change Committee (CCC) and a scoping study commissioned by the former Department for Business, Energy and Industrial Strategy, the government is developing a new methodology to increase its accuracy, robustness, and ensure it is fit net zero.
In December 2023, we published a consultation on this new methodology – the Home Energy Model (closing on 6 March 2024) – so that industry can participate in the ongoing development process.
The Home Energy Model is still under development and its first version will be implemented alongside the Future Homes Standard in 2025.