Specifying Electrorad products with ‘SAP’

the government Standard Assessment Procedure


What is SAP?

SAP stands for ‘Standard Assesment Procedure’ and is the government standard for assessing the energy efficiency of properties. Every new build property has to meet pre determined SAP target scores. From the SAP assessment an EPC ‘Energy Performance Certificate’ can be generated.

How does SAP work?

Within SAP every product or material used in the building of a property is rated for energy efficiency. The ratings are compiled by the government in conjunction with BRE ( Buildings Research Establishment ). All products and materials are entered in to the SAP equation and a property energy efficiency rating and carbon emission rating is generated.

Electric Radiators & SAP

Electric radiators are included within SAP as an option for the primary heating of a property. Electric radiators are rated in SAP as 100% energy efficient and very responsive. There are options for which electricity tariff to use. If a standard tariff is specified, then the running costs are calculated as quite high and a poorer score is achieved. Economy 10 tariff can be selected and this allows in SAP for 50% of the running costs to be calculated at cheap rate electricity resulting in more favourable theoretical running costs and a more favourable SAP score.

Whichever electric radiators you choose, the SAP rating is the same. This is due to the conversion of electricity to heat being always 100% efficient in all electrical resistance element heating. The material the radiator is made from i.e. Aluminium or Steel and what is inside the radiator ( fluid, oil, water, fireclay, brick, etc ) does not make any difference to the energy efficiency or the SAP rating. These different materials only make small differences to the responsiveness of the radiators i.e. faster or slower heat up times.

The carbon emissions in SAP from using electric radiators are unfortunately deemed to be quite high. At the point of use there are no carbon emissions but the U.K. power stations are typically burning fossil fuels to create electricity and this is a very inefficient process. Only around 40% of the fuel burned is converted to electricity. It is theoretically possible for an electric radiator system to be carbon neutral by using or specifying electricity from renewable sources i.e. solar, wind, wave, nuclear etc. SAP does not currently have any way to account for this choice. It is assumed that regular grid electricity is used and currently 51% of that electricity is from gas turbine power stations.

Holistic view on specification

Specifying electric radiators will give a less favourable SAP score than specifying an A rated gas boiler heating system. In order to meet the overall SAP target, other factors need to be looked at. You may need to add more ‘positives’ to outweigh the ‘negative’. For example – extra insulation, higher energy efficiency rated windows and doors, solar thermal, solar PV. Generally lower U value materials for the external envelope will go a long way to achieving the target.