What Are SAP Calculations? A Beginner’s Guide

New Build Technical Drawing Used for SAP Calculations

When undertaking a new build construction of properties or an extension on your home, there are a lot of things you need to consider to ensure your building is compliant with all current Building Regulations. One of the most important considerations for your property development is a SAP calculation (Standard Assessment Procedure).

If you’re not sure what this means, or whether you actually need SAP calculations or not, take a look at our guide below. Where we go into detail about what a SAP calculation actually is and who needs one according to Building Regulations.

At Falcon Energy, we’re fully qualified to undertake all aspects of SAP calculations, including for new build developments, extensions and conversions. Give our team a call on 01403 253439 to find out more.

What are SAP calculations?

SAP stands for Standard Assessment Procedure and refers to the process of calculating and determining the energy performance of buildings and homes. This predicted energy assessment will be used to help calculate the EPC rating once the property has been finished.

SAP calculations are a government requirement under Building Regulations and are based on drawings, plans and specifications of a
new build property. The building will be given a score between 1 and 100, with 100 being the most energy efficient.

These calculations allow you to see how energy efficient a development will be before it has been built, to ensure that all developments comply and meet modern energy and environmental standards. It will also give you an idea of any energy running costs of the property.

Do I need a SAP calculation for an extension or conversion?

Although typically only needed for new builds or developments, in some cases you may also need to get SAP calculations done when having an extension on your home or a conversion.


When it comes to getting an extension on your home, whether or not you need a SAP calculation report depends on the amount of glazing that is incorporated in the new build. Building Regulations state that if the total area of new glazing exceeds 25% of the total floor area of the new extension, then you will need to get a SAP calculation.

Homeowners these days tend to prefer extensions that let in a lot of light and incorporate elements such as bifold doors and skylights in the plans, which means that extensions do tend to exceed this amount and need to have SAP calculations to comply with Building Regulations.

Lots of glazing in a property can have an effect on its energy efficiency rating and the carbon emissions produced. SAP calculations ensure that your extension will have a minimal environmental impact rating.


The rules are slightly different for conversions and SAP calculations are only required if the conversion results in a ‘Material Change of Use’ or a ‘Change of Energy Status’.

A material change of use refers to a property that is changing the purpose for which the building is used, such as converting a dwelling into a number of flats.

A change in energy status refers to buildings or spaces that have not previously been heated being changed to be heated in the future.

If either or both of these changes occur, then you will need to get SAP calculations for your conversion.

Change of Use Property from Office to Flat

How are SAP calculations undertaken?

To complete a SAP calculation and understand the energy performance and energy cost of a development, there are a number of factors an assessor needs to have access to, these include:

  • Floorplans of the build
  • A full site plan of the development
  • Elevation drawings
  • Sectional drawings
  • Details of the insulation type that will be used and it’s thickness
  • Details of the u-value of openings such as windows and doors
  • Details of which heating systems are being used
  • Details of the boiler system
  • Details of any ventilation systems that will be installed
  • Details of any renewable technologies being used

Depending on whether you’re having a new build, extension or conversion done, the way that SAP calculations are completed may differ slightly, but in general, this information will be used to create a calculation that will show the energy efficiency of the dwelling.

What is the difference between a SAP and an EPC?

Whilst both SAPs and EPCs (Energy Performance Certificate) both calculate the energy efficiency of a property or building and give it a rating, there is a fundamental difference to how they work and how they are calculated.

SAPs are purely for new build developments, properties and some extensions. They are calculated using special software and are based on the plans and measurements provided by the architect.

EPCs are for existing homes and buildings and look at things such as

  • the type and age of the property
  • the water and heating systems used
  • any insulation
  • types of lighting and glazing in the property

All of these factors are assessed and entered into a calculation programme that will use this information to provide an accurate energy assessment rating.

Both of these must be undertaken by a professional and qualified company or individual.

Who performs SAP calculations?

It is important that you instruct a qualified SAP calculation assessor as early on into the process as possible. This way, you can ensure all materials, designs and plans are as energy efficient and compliant as possible right from the very beginning. The later that you instruct someone, the more costly it can be to alter plans if they don’t comply with regulations.

At Falcon Energy, we are energy experts and qualified SAP calculation assessors. This means we are able to provide valuable information and advice about the different aspects of energy efficiency, as well as undertake all SAP calculations at your development.

Get in touch

If you would like to find out more about our SAP calculation services or would like to speak to one of our team members about energy advice for your property development, get in touch on 01403 253439 and we would be happy to help.

Posted in Energy, EPC's.