Thermal image of window/wall junction thermal bridge

SAP Assessment and EPCs (Energy Performance Certificates)

SAP energy assessment is used as part of building control approval, in two stages: Design Stage, and As Built. An EPC is issued at As Built stage. There is more detail about the process further down this page.


Prices for SAP assessment are dependent on the size and complexity of each project. A full quote will be provided once plans for a project have been inspected.

As a rough guide, prices for Design Stage can range from £150 to £250 for simpler projects, but may be more or less than that depending on the amount of work involved. A quote will always be agreed before work is undertaken.

Provided there are no major changes between the Design and As Built stage, then preparing As Built SAP and issuing an EPC usually costs £40.

In order to complete a SAP assessment full scalable plans and specifications are needed, including floor plans, elevations, and sections, along with details of construction, heating and hot water systems, renewables energy installations, ventilation strategy, lighting efficiency, window/door type and intended U-values etc.

Do I need SAP Calculations?

SAP is used to show compliance with the Building Regulations for energy efficiciency (Part L1A and L1B in England and Wales, Section 6 in Scotland). It applies to new dwellings, some extensions, and conversions or major refurbishments (SAP is short for the UK Government’s Standard Assessment Procedure for the Energy Rating of Dwellings).

How is compliance with the regulations demonstrated?

A SAP pass is achieved when the Dwelling Emission Rate (DER) and Dwelling Fabric Energy Efficiency (DFEE) (calculated by SAP) are below the Target Emission Rate (TER) and Target Fabric Energy Efficiency (TFEE) for that property.

  • The DER gives the environmental impact of a building based on CO2 emissions per square metre of floor area.
  • The DFEE essentially expresses how well insulated the building is, giving the energy consumption per square metre of floor area.
  • The target rates are set by SAP software, derived from the size and surface areas of the property and the maximum allowable emissions and energy use of that property according to the Building Regulations.

Energy Performance Certificate (EPC)

Energy Performance Certificates (EPC) are generated when a project is built, giving energy and emissions ratings rated from ‘A‘ (very energy efficient, low emissions) to ‘F‘ (very poor energy efficiency, and high emissions).

The Annexe, West Dorset

The two stages of SAP

Assessments happen in two stages, ‘Design Stage’ and ‘As Built’.

  • At the Design Stage a Regulations Compliance Report and Predicted Energy Assessment (PEA) are produced, demonstrating that the building complies with the Building Regulations or indicating the areas where improvements are needed in order to comply.
  • The PEA resembles an EPC and indicates likely energy cost and emissions. Draft calculations can be provided before the final report is issued, allowing for information to be checked and for plans to be changed before submission to your building control officer.
  • The As Built stage compares the original plans to any changes made during construction, making changes to SAP inputs where necessary before issuing an Energy Performance Certificate (EPC).
  • A draft EPC can be issued first allowing you to check data, and to allow final on-site adaptations to be made if necessary before final lodgement of the EPC.
  • Final EPCs are lodged with the EPC register at in England and Wales, or in Scotland