Lighting in SAP 10

What are the changes?

SAP 10 has a new approach towards lighting and the associated energy use. Where as before SAP 2012 looked at the percentage of low energy of lighting in relation to the total number of light fittings, SAP 10 now has a more detailed approach. This new approach means energy use from lighting can now be more accurately assessed within the SAP calculation and final EPC.

It is now a requirement for the SAP calculation to include a schedule of all lights within the dwelling and looks at the associated energy use for each specific type.

SAP 10 now compares the provided capacity of fixed lighting with a reference capacity range based on the dwelling’s floor area. A range is used to allow some flexibility for different lighting designs and dwelling layouts.


If the lighting capacity provided is less than the bottom of the reference range, additional top-up lighting (of poor efficacy) is assumed to be used to meet the shortfall. If more is provided than the top of the reference range, the surplus is assumed to be used (using the actual efficacy). In both cases this is likely to lead to an increase in predicted lighting energy. Lighting energy is therefore minimised where the provided lighting capacity is within the reference range and supplied by lamps of a high efficacy.

What's does this mean to me?

This now means we as assessors require more detail than before about the proposed lighting within the dwelling. For a lot of clients this means either by way of a detailed lighting design or written specification you'll need to provide this information so we can better understand the different types and quantity of lighting within the dwelling both at stage stage and provide evidence upon completion at the As Built stage.

Unfortunately not providing this information will results in default figures being used within the SAP calculation and will most likely result in a compliance failure. Below is a visual illustration of the effects of the each option.

We therefore suggest you use a lighting schedule and detail per room the total number, type and efficacy of the lights you intend to provide. Additionally, this should be provided to the electrician to ensure what they purchase and install is in compliance with the lighting efficacy used by the SAP calculation and energy performance certificate.

What do i need to know?

You'll now need to provide detailed information about the light fittings within the dwelling, this will include the following:-

Quantity of light fittings

Type of light fittings

Luminous Efficacy (Lumen per circuit Watt) - (lm/W)

Lumens per circuit Watt is a value which determine the efficiency of the light fitting. This can be calculated by dividing the Lumen's of the lighting fitting by the Watts used of light fitting. The higher the luminous efficacy the better for your SAP calculation and dwellings energy performance.

What are typical values for standard lamp fittings?

Below is the Table L1 extracted from the SAP 10 methodology and details the default luminous for lamp types:-

Lumens/Watt (lm/W)
Linear Fluorescent
Compact Fluorescent
Halogen Low Voltage
Halogen Lamps

How to evidence for As Built Stage & EPC?

As well as providing a detailed lighting schedule we recommend you provide an "As Built" plan showing the installed lighting which can easily be used by our assessor to confirm the quantity and type of different light fittings.

We have developed a simple online form for our customers to use and easily submit evidence to us. To use the form ensure you are logged into our members area and use the following link