KJ Tait

Minimum Standard for Domestic EPCs

3 November 2023

The Minimum Energy Efficiency Standards (MEES for short) has been in place in England for a number of years, this currently mandates a minimum standard of EPC for assured/regulated tenancy agreements of at least an EPC ‘E’.  


However, this standard is to be strengthened to EPC ‘C’ by 2025.  In Scotland, there is an expectation that EPC ‘C’ will be mandated for lettings by 2028 at the latest.  


Why does all this matter? Currently there are two metrics on a domestic EPC, the Energy Efficiency Rating (EER) often referred to as the ‘SAP’ rating and the Environmental Impact Rating (EIR).  It is the SAP rating that will be the subject of the minimum standard.  This is a cost metric where the unit rates for grid electricity and gas are prescribed from the Standard Assessment Procedure (SAP) process of conducting dwelling assessments, under SAP10.2 these are 16.49p/kWh and 3.64p/kWh for electricity and gas consumption respectively.    


The result of using this metric (and theses costs) means that for a dwelling that has heating supplied via a heat pump, to get the same rating as a gas fired boiler building, neglecting the small affect of the boiler efficiency, a heat pump with a seasonal efficiency of around 4.53 would be required.  Our experience suggests that this would not be achieved by any products on the market for heating systems supplying a radiator system at 55 degrees C.   Therefore, in most cases installing a heat pump over a gas fired boiler system would make the EPC for the dwelling worse.  For a new building, the dwelling may just achieve a ‘C’, however for the existing stock this would likely mean at best a ‘D’.    


For direct electric systems such as electric panel heaters and electric boilers, the result is worse with ratings of ‘E’ and below expected.    


We need Governments to review this minimum standard and/or overhaul the domestic EPC system.  The resultant worsening of the SAP rating by decarbonising heating systems goes against the efforts the industry is currently making.  We would advise that the minimum standard is placed on the EIR rating instead as this would improve as dwellings are decarbonised.