A dozen Which? members and homeowners across England, Wales and Scotland booked EPC assessments on their behalf during February to March 2024 to find out how accurate EPCs are.

Their properties were built between 1650 and 1999 and ranged from a one-bedroom flat to a five-bedroom detached house. Which? subsequently uncovered issues with the accuracy of the results and the recommendations that the homeowners received.

One homeowner had their EPC survey done, but never received their certificate. The survey fee was refunded, but the homeowner was left in the dark about their home’s energy efficiency.

Of the remaining 11 participants, just one was ‘very satisfied’ with their EPC and only three said they were likely to recommend getting an EPC based on this experience.

Most participants (73%) told Which? their EPC did not appear to be accurate – they said the descriptions of key aspects of their home like the windows, roofs and heating systems were incorrect.

Several participants also felt that the recommendations suggested were unaffordable. One consumer said that they felt draught proofing was overlooked in their EPC report despite their home having an open chimney and front door with single glazing.

Peter and Carol Vermeulen in Aberdeenshire achieved a D rating for energy efficiency for their 1980s four-bedroom semi-detached bungalow in Aberdeenshire following their EPC assessment.

On receipt of the EPC, however, they noticed several discrepancies. There was no mention of their solar PV or solar thermal panels, or of a wood-burning stove. The suspended floor was described as uninsulated, although they had discussed their underfloor insulation with the assessor during the survey and offered to open an inspection hatch so this could be checked.

Which? contacted the assessor to point out the mistakes. After checking his survey notes, he admitted that there were omissions (which he blamed on the software) and offered to supply a new EPC. The assessor issued a new, corrected EPC, with an improved B rating for energy efficiency.

The consumer champion is calling for the next UK government to reform EPCs – though the Scottish Government has responsibility for EPCs in Scotland.

Rocio Concha, Which? director of policy and advocacy, said: “With millions of families worried about high energy bills and the UK facing a big challenge to transition to low carbon heating, energy performance certificates could be a helpful tool for consumers looking to save money and improve their home’s efficiency in the future.

“However, our research shows they are in desperate need of reform – with current certificates often inaccurate and only suggesting costly improvements with long pay back periods. The next government must make energy performance certificates a more reliable and useful tool for householders.

“This should include reviewing the auditing and training requirements for domestic energy assessors and ensuring EPCs provide relevant information and clear, actionable advice for consumers.”