More than half of homes across England and Wales have an EPC rating of D or below, highlighting the scale of the retrofit challenge facing homeowners and landlords ahead of tougher future energy efficiency standards.
Analysis from Emperor Paint, based on Department for Levelling Up, Housing and Communities data covering EPC certificates issued between January 2008 and February 2026, found that 55% of homes fall into EPC bands D to G.
Under proposed reforms, rental properties in England and Wales will eventually need to achieve the equivalent of an EPC rating C, with the changes expected to apply to tenancies from October 2030.
The Government is also preparing to overhaul the EPC system itself, replacing the current model with four separate metrics covering fabric performance, heating systems, smart readiness and energy costs.
AGEING HOUSING STOCK
The research suggests ageing housing stock, poor insulation and outdated heating systems continue to be major factors behind lower EPC ratings.
An EPC rating of D is considered average energy efficiency, while E, F and G ratings reflect increasingly poor thermal performance, inefficient heating systems and limited insulation.
The Isles of Scilly was found to have the highest proportion of energy inefficient homes, with 84.97% of properties rated D or below. Gwynedd ranked second at 74.32%, followed by Pendle at 74.05%.
Other areas with high concentrations of lower-rated homes included Ceredigion, Castle Point, Blackpool and Barrow-in-Furness.
Now incoming changes to EPC methodology could also make achieving higher ratings more difficult for many homeowners and landlords.
HOME ENERGY MODEL
Jack Reading of Emperor Paint says: “Changes to energy performance certificates mean that they will now be based on how properties retain heat, rather than how much energy a property uses.
“The new system, the Home Energy Model (HEM), will measure smart readiness, heating systems, fabric performance and energy cost.”
He also argues that external wall performance remains an overlooked factor within the current EPC framework.
Reading says: “The vast majority of exterior walled surfaces are porous, meaning that they can become saturated with water. Research suggests damp content of 5% can lower the insulating properties of a surface by as much as 50%.
“This means that when the exterior walls of homes become saturated with water, it can lead to an increase in heat loss.”
GROWING GAP
According to Emperor Paint, super-hydrophobic masonry coatings can reduce water absorption and improve thermal performance, although such measures are not currently reflected within EPC calculations.
Reading adds: “As weather conditions become more extreme, with warmer summers and wetter winters, exterior wall coatings not being included in EPC ratings under ‘Fabric Performance’ represents a growing gap in how home energy efficiency is measured in the UK.
“Without accounting for how walls perform in real, weather-exposed conditions, EPC scores risk overlooking a key factor influencing heat loss.”
