What Are SAP Calculations? A Beginner’s Guide

New house build

When undertaking an extension on your home, or a development of properties, there are a lot of things you need to consider to ensure your building is compliant with all regulations. One of the most important considerations for your property development is a SAP calculation.

If you’re not sure what this means, or whether you actually need one 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.

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.

They 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.

Do I need a SAP 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 SAP calculations done.

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 done.


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.

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 just 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 does SAP calculations?

It is important that you instruct a qualified SAP 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.

At Falcon Energy, we are energy experts and are able to provide valuable information and advice about the different aspects of energy efficiency to ensure that your development is as efficient and compliant as possible from the start.

The later that you instruct someone, the more costly it can be to alter plans if they don’t comply with regulations.

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, get in touch on 01403 253439 and we would be happy to help.

Posted in Energy, EPC's.