The body representing assessors who carry out energy performance certificate testing has challenged some of the findings in a report led by Atom Bank on the real scale of carbon emissions.

Released today, the study by Atom in conjunction with Experian and the University of Durham, concluded that UK banks could be over-estimating the carbon emissions from homes on their mortgage books by as much as 50%.

It suggested that this was due to their reliance on EPC assumptions to calculate emissions, rather than meter readings.

The research also found that there was not a significant difference in emission between homes with the best and worst EPC ratings.

But the The Property Energy Professionals Association, which represents the energy assessors who give homes their EPC ratings, has warned against throwing out the scheme.

It has also pointed to the downsides of the study’s focus on meter readings as an alternative way of measuring emissions. 

PEPA chair Andrew Parkin says: “EPCs are based on standardised assumptions and use carbon intensity data available at the time of assessment. 

“As the UK’s energy mix evolves—particularly with the decarbonisation of electricity—the carbon factors used in EPC calculations can become outdated. 

“The EPC Reform Consultation is examining whether we need to reduce the 10-year validity period of EPCs and this research suggests that they should be significantly reduced.”

PEPA is in support of reducing it to three or five years.

Parkin also points out that occupancy levels and behaviour of home owners are not captured in EPCs.

He says: “It is critical to recognise that EPCs do not measure actual energy consumption. 

“They estimate the energy required to maintain a reasonable level of comfort in a property, assuming standard occupancy and usage patterns.

“Comparing EPC estimates with actual meter readings conflates two fundamentally different metrics.

“Actual usage is influenced by occupant behaviour, affordability and lifestyle choices—none of which EPCs are designed to capture.”

Parkin says the observation that homes across EPC bands A to G may use similar amounts of energy is “intriguing but must be interpreted with caution”. 

Financial restrictions might mean that those in lower-rated properties, particularly those housing families in fuel poverty, use less energy.

He says: “These households may under-heat their homes, leading to lower actual consumption but poorer health and wellbeing outcomes. 

“EPCs estimate what energy should be used to achieve comfort—not what is actually spent.”

Parkin argues that policymakers and stakeholders should not focus solely on actual energy use in the drive towards net zero. 

He says: “EPCs play a vital role in identifying where improvements can be made to reduce energy demand and improve building performance.”