Standard Assessment Procedure
Guidance on how a home's energy performance is calculated using the Standard Assessment Procedure (SAP) methodology, which underpins the Energy Performance Certificate (EPC).
Overview
The Standard Assessment Procedure (SAP) is the methodology used by the government to assess and compare the energy and environmental performance of dwellings. Its purpose is to provide accurate and reliable assessments of dwelling energy performances that are needed to underpin energy and environmental policy initiatives.
The government is committed to increasing the accuracy of SAP. The most recent update of the SAP 10.2 specification (published 15 December 2021) is available on the BRE website. The next version of SAP 10 (10.2) comes into force with the updated Part L Building regulations in Summer 2022, and will incorporate various changes to the methodology, including updated:
- fuel prices
- CO2 emissions
- primary energy factors
For existing buildings, a simplified version of SAP called Reduced Data SAP (RdSAP) is used to assess the energy performance. An RdSAP assessment will use a set of assumptions about the building based on conventions and requirements at the time the building was constructed. Government is working on an RdSAP update which we expect to publish in Spring 2022.
Background
SAP was developed by the Building Research Establishment (BRE) for the former Department of the Environment in 1992, as a tool to help deliver its energy efficiency policies. The SAP methodology is based on the BRE Domestic Energy Model (BREDEM), which provides a framework for calculating the energy consumption of dwellings.
In 1994 SAP was cited in Part L of the Building Regulations as a means of assessing dwelling performance. Reduced Data SAP (RDSAP) was introduced in 2005 as a lower cost method of assessing the energy performance of existing dwellings. SAP, RDSAP and BREDEM are used to underpin the delivery of a number of key energy and environmental policy initiatives, for example:
- Buildings Regulations for England and Wales and the Devolved Administrations
- Energy Performance Certificates (EPCs). The SAP methodology underpins the EPC, which can only be produced by a qualified and accredited assessor. Domestic Private Rented Sector Regulations set standards using EPCs for the energy performance level at which homes can be rented out
- EPCs are needed for the Domestic Renewable Heat Incentive (Domestic RHI), the government financial incentive that promotes the switch to renewable heating systems. Under the RHI scheme regulation, applicants must produce an EPC, which proves it’s a residential building and provides the level of detail required to calculate Domestic RHI payments
How SAP works
SAP works by assessing how much energy a dwelling will consume when delivering a defined level of comfort and service provision. The assessment is based on standardised assumptions for occupancy and behaviour. This enables a like-for-like comparison of dwelling performance. Related factors, such as fuel costs and emissions of carbon dioxide (CO2), can be determined from the assessment.
SAP quantifies a dwelling’s performance in terms of: energy use per unit floor area, a fuel-cost-based energy efficiency rating (the SAP Rating) and emissions of CO2 (the Environmental Impact Rating). These indicators of performance are based on estimates of annual energy consumption for the provision of space heating, domestic hot water, lighting and ventilation. Other SAP outputs include estimate of appliance energy use, the potential for overheating in summer and the resultant cooling load.
SAP 2012
Until Summer 2022, SAP 2012 is the version that will be used to demonstrate building regulation compliance and produce EPCs - see the SAP 2012 and 2009 versions:
Future developments - SAP 11
In 2020 we commissioned a scoping project for the next version of SAP - SAP 11 - to advise on how it can be enhanced to support net zero commitments for buildings. A consortium led by Etude carried out the SAP 11 scoping project which made a number of recommendations, including how to make SAP more accurate, robust and fit for purpose to support the net zero commitment.
In October 2021 we appointed a consortium of experts led by Building Research Limited (BRE) to develop, test and communicate SAP / RdSAP 11. The SAP 11 project team is working with stakeholders to consider the Etude recommendations and how to implement them. We will engage with industry as the project progresses via our existing SAP Industry Forum.
SAP / RdSAP 11 will come into force in 2025, alongside the Future Homes Standard update of the Building Regulations.
Last updated 16 December 2021 + show all updates
-
Updated with information about SAP 10.2 which comes into force in summer 2022, and SAP 11, planned for 2025.
-
Minor updates to the guide on SAP adding in new links to BRE.
-
First published.