What Is SAP? — Standard Assessment Procedure

Definition

SAP (Standard Assessment Procedure) is the UK government's methodology for assessing and comparing the energy performance of dwellings. Developed by the BRE (Building Research Establishment) on behalf of BEIS (now DESNZ), SAP provides the calculation framework used to demonstrate compliance with Part L of the Building Regulations and to generate Energy Performance Certificates (EPCs) for all UK homes.

When Is It Used?

SAP is used at two key stages of every new dwelling: at design stage to demonstrate that the proposed design meets Part L targets, and at completion (as-built stage) to confirm compliance and generate the EPC. RdSAP (the reduced-data version) is used whenever an EPC is needed for an existing home being sold, rented, or assessed for grant eligibility. SAP results also feed into the Target Emission Rate (TER) and Target Primary Energy Rate (TPER) calculations that determine Part L compliance.

Key Facts

• Current version: SAP 10.2 (in use since June 2022 with Part L 2021)
• SAP score range: 1 to 100+ (higher = more energy efficient, lower running costs)
• Two compliance metrics: Target Emission Rate (TER) and Target Primary Energy Rate (TPER)
• SAP 10.2 uses updated electricity carbon factors, favouring heat pumps and electric heating
• The PCDB (Product Characteristics Database) provides boiler and heat pump efficiency data
• Thermal bridging: default y-value (0.15), ACDs (0.08), or calculated psi-values can be used
• Airtightness test results feed directly into the as-built SAP calculation
• The Home Energy Model (HEM) will eventually replace SAP as the primary assessment method

Related Calculators

Use the U-Value Calculator for fabric inputs to SAP, or the EPC Rating Estimator for approximate ratings. See also the EPC glossary entry, Thermal Bridge glossary entry, and the Part L U-Values reference table.