The firm analysed EPC lodgement data from 589,549 certificates issued during 2026 to assess how energy efficiency varies by property size, type and tenure.
The research found that properties with two or three habitable rooms currently hold the highest average EPC score at 70.2, placing them within the current EPC C banding of 69 to 80.
Larger homes recorded lower average scores, with properties containing more than nine habitable rooms averaging 63.0, within EPC D territory.
Flats recorded the strongest energy efficiency performance among property types, with an average EPC score of 72.8. This compared to average scores of 70.1 for maisonettes, 70.0 for houses and 67.6 for bungalows.
Privately rented homes also performed slightly better than owner occupied properties. The average EPC score for privately rented homes stood at 68.9, compared to 68.1 for owner occupied homes.
Rushbrook & Rathbone said the findings suggest many landlords, particularly those with smaller rental homes and flats, may already be close to meeting future EPC requirements without major additional investment.
However, the firm said landlords would still need to maintain standards as regulation within the private rented sector continues to evolve.
Roma Sharma, managing director at Rushbrook & Rathbone, said: “There has understandably been a great deal of concern amongst landlords regarding proposed EPC requirements and the potential cost of bringing properties up to standard.
“However, what this data suggests is that many landlords may already be in a far stronger position than they expect, particularly those with smaller rental homes or flats, which naturally tend to perform better from an energy efficiency perspective.
“Over recent years, many landlords have already invested in improvements such as upgraded heating systems, insulation, glazing and lighting, often as part of wider refurbishment and maintenance programmes.
“That said, compliance is rarely something that can simply be dealt with once and then forgotten about. Standards, legislation and assessment methodologies continue to evolve, particularly as the private rented sector becomes more regulated.”
