What Are SAP Calculations?

SAP is short for ‘Standard Assessment Procedure’ and refers to the process of calculating the energy performance of new houses and buildings. The Building Regulations require all new dwellings to have SAP calculations before any work is completed, and homeowners and property developers must understand their legal responsibilities.

 Here is everything you need to know about SAP calculations and why we need them.

Why are SAP calculations required?

SAP calculations are required to produce a new Energy Performance Certificate (EPC). An EPC scores a property from A-G based on its energy efficiency, with A being the most efficient and G being the worst. All properties in the UK must have an EPC before a residential property can be sold or rented. From 1st April 2018, it became illegal to rent a property with an F or G EPC rating.

Building Regulations require that a SAP calculation and a predicted energy assessment are submitted before new dwellings are built or sold. A SAP assessment gives new buildings a score of between 1 and 100, with 100 being the most energy-efficient. These regulations were introduced as part of the government’s plan to lower carbon emissions and fight fuel poverty.

When is a SAP calculation needed?

SAP calculations are usually only required for new builds and property developments. However, you may also need to have a SAP calculation report if you are planning on extending or converting your existing property.


A SAP calculation report is not required for extensions as long as areas of new glazing account for 25% of the new floor area or less. This rule helps to maximise energy efficiency as glazing loses more heat than walls. You will need to have a SAP assessment carried out if your planned extension does not meet this requirement. 


A SAP calculation report is only required for conversions if the planned work will result in a ‘Material Change of Use’ or a ‘Change of Energy Status’. For example, if you plan to convert an unused barn or convert an existing single dwelling into apartments. You will need to produce SAP calculations to demonstrate the energy performance of the new building.

How are SAP calculations completed?

A SAP assessor will conduct an assessment of your new dwelling based on the following:

  • The elements of structure
  • The heating and hot water system
  • The internal lighting
  • The renewable technologies used in the home

SAP calculations are a desktop exercise, not a site survey. You must therefore provide the SAP assessor with as much information as possible about the new dwelling. This should include details of floor plans, elevations, insulation, hot water generations, renewable technologies, and more. The SAP assessor will help you create a design that will suit the current Building Regulations.

Your property will then be given a SAP score of between 1 and 100. The higher the score, the more efficient your property is and the lower your energy costs will be. It is recommended that the SAP calculation report is completed early in the planning process, to help avoid any delays or expensive redesigns.

Tips for passing the SAP assessment

The good news is, there are plenty of things you can do to improve your SAP score and pass your SAP assessment the first time. Think carefully about your design and incorporate eco-friendly technology like low energy lighting. Energy-efficient lights use between 25% and 80% less energy than traditional light bulls. Using low energy lighting will boost your SAP score and save you money on electricity.

You should also choose high thermal performance windows to reduce heat loss. Energy-efficient windows are designed to keep your home warmer in the winter and cooler during the summer months. This means that you’ll have less reliance on heating and cooling systems that use a lot of energy.

Another simple way to improve your SAP score is by installing an efficient boiler. Take the time to research different boilers and choose the most eco-friendly design for your new dwelling.


There are a lot of things to consider when planning a property development or extending your home. Homeowners and property developers must ensure that any planned work is legally compliant.

Building Regulations require all new properties to have a SAP calculation report to demonstrate the energy performance of new residential buildings. Get in touch with your local energy specialists if you need more guidance on the SAP calculations and energy requirements.

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