KJ Tait

Domestic EPC Standards

19 October 2022

SAP10.2 is now in force in England and will be in force in Scotland from December.  It has been a long road to get here but already there have been issues with the software of accreditation bodies and issues with results.  For those who are not aware, a domestic EPC has two ratings: the Environmental Impact Rating (EIR) and the Energy Efficiency Rating (EER).  The EIR is built upon the energy used to heat the dwelling, provide hot water and to ventilate.  These energy consumption figures are multiplied by gas and electricity carbon factors to produce a benchmarked rating.  The EER is similarly built upon the energy used within the dwelling but is multiplied by set costs for gas and electricity to produce a benchmarked rating.  It is the EER that is subject to minimum standards legislation of EPC ‘C’ in both England and Scotland.


Under SAP10.2, for those buildings heated via electricity, there is a significant improvement in the EIR due to a circa 400% reduction in the carbon factors of electricity.  For the EER, the rating which matters legislatively, a move to electrify buildings will not improve an ‘EPC Rating’; indeed, many get worse after replacing gas boilers.  This is due to the costs within the SAP document for grid electricity (16.49p/kWh) and gas (3.64p/kWh).  Anyone paying an electricity or gas bill will know that these figures are now out of date and may need refreshed in future.  However, even for a heat pump installation, to achieve an improvement in the EER, the heat pump would be required to have an efficiency of at least 450%.


This is a high level assessment; factors such as the efficiency of the boiler have not been taken into account.  It does represent the scale of the challenge; should we be now looking towards the EIR as the main driver for change?  Perhaps, and if gas and electricity prices are decoupled (and electricity decreases in price), the argument for doing this could be even greater as the primary objective of the EER is to reduce fuel poverty.