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The full UK energy calculation methodology that’s used for residential properties
The Standard Assessment Procedure (SAP) is the UK methodology used to assess the energy and environmental performance of residential property.
Its purpose is to provide accurate and reliable assessments of property energy performances that are needed to underpin energy and environmental policy initiatives.
It’s important to realise that the SAP is in fact two things. Firstly it’s a procedure that calculates many many outputs – such as primary energy demand, space heating demand, running costs and carbon emissions to name just a few. But it also generates a “SAP Rating”. This rating is a running cost index on a scale of 1 to 100, and is used as the basis for the A to G rating on EPCs.
Many people think that the SAP is not a good measure of carbon since it’s running cost based. This is true if you’re talking about the SAP Rating. But the SAP procedure itself it very capable of calculating carbon emissions and has been doing just that since its inception in the early 1990s!
The government is committed to increasing the accuracy of SAP. The latest version of SAP 10 (10.2) came into force with the updated Part L Building regulations in Summer 2022, and incorporates various changes to the methodology, including:
For existing buildings, a simplified version of SAP called Reduced Data SAP (RdSAP) is used to assess the energy performance.