Are EPC's a reliable indicator of a Property's Energy Efficiency?

Study Reveals Energy Performance Certificates (EPC) Not Reliable for Assessing Energy Efficiency

A recent study conducted by Switchee, a social housing data and insights company, has challenged the reliability of Energy Performance Certificate (EPC) scores as indicators of energy efficiency and heat retention in properties. The study, which analyzed data from 10,000 properties using Switchee devices installed in UK social housing homes, found that EPC ratings have no impact or correlation with the energy performance of a home.

To assess the energy performance of the properties, Switchee utilized real-time data captured by multiple sensors within its devices, measuring the time taken for properties to lose 1°C of internal air temperature when the heating was turned off. Surprisingly, the data revealed that the best-performing homes were classified as EPC A, F, and G, with an average Heat Loss Rate (HLR) of just under 6 hours. On the other hand, the worst-performing homes were classified as EPC C and D, with an average HLR of 4 hours.

The study also highlighted a significant variation in HLR measurements, with the worst-performing property losing 1°C of heat in less than an hour, while the best-performing property retained heat for over 9 hours. This discrepancy in heat loss has a direct impact on residents, leading them to heat their homes for an average of 1 hour and 48 minutes longer than those living in homes with a lower HLR. In terms of costs, this amounts to an additional £1,576 per year in heating expenses.

Contrary to the common belief that property archetype, such as mid-terrace or end terrace, affects heat retention, the Switchee study demonstrated that it has minimal influence. Instead, the level of insulation and ventilation in homes emerged as key factors affecting heat loss. External weather conditions in a particular area also play a role, with homes in colder regions experiencing quicker heat loss than those in warmer areas. Property occupancy levels also contribute to variations in HLR measurements.

EPC scores have gained increasing importance for social housing landlords as they strive to meet new targets. The Clean Growth Strategy has set targets for social housing properties to achieve EPC band C by 2030 for fuel-poor homes and by 2035 for all social housing. However, the study's findings suggest that energy efficiency targets may be focused on the wrong factors.

Instead of relying solely on EPC ratings, the study proposes that housing providers consider a property's Heat Loss Rate (HLR) score. This approach enables providers to allocate retrofit resources to the properties that genuinely require them, rather than those presumed to be in need. Additionally, by analyzing the HLR before and after retrofit measures, the impact of these measures can be accurately assessed using real data from the homes.

Switchee CEO Tom Robins expressed concern over the findings, stating, "Our data suggests not" when questioning whether social housing providers can confidently rely on EPC ratings alone to evaluate the energy efficiency of their housing stock. Having analyzed over 8 billion data points, Switchee's study emphasizes the effectiveness of insulation and the importance of maintaining an airtight property.

To support housing providers in assessing energy efficiency, Switchee has collaborated with them to develop the Heat Loss Rate (HLR) metric, which is available through the Switchee analytics dashboard. By adopting this alternative approach, housing providers can make more informed decisions regarding retrofit measures and improve the overall energy efficiency of their housing stock.