The recently published EPC Accuracy Report provides one of the most detailed investigations yet into why Energy Performance Certificates (EPCs) sometimes differ from a property’s actual energy use. While much of the report focuses on identifying the causes of these gaps, it also offers valuable insight into potential future improvements to EPCs and the wider energy assessment process.
Importantly, the report does not conclude that EPCs are ineffective. Instead, it highlights a range of opportunities to improve their accuracy and ensure they better reflect the current state of properties. This investigation will support the ongoing development of the Home Energy Model (HEM), which is expected to replace SAP as the core calculation methodology behind future EPCs.
More Dynamic and Up-To-Date EPCs
One of the most significant findings in the report is that many properties have undergone energy efficiency improvements since their EPC was originally produced. The researchers found that these post-EPC upgrades accounted for more than half of the reduction in the performance gap when calculations were updated.
As a result, one of the most notable future improvements to EPCs could be the introduction of more dynamic updates. Rather than relying solely on a new assessment every time a certificate expires or a property changes hands, EPCs could potentially be updated automatically when certain regulated improvements are recorded.
The report suggests that datasets such as the National Energy Efficiency Data-Framework (NEED) could help make this possible, allowing EPCs to better reflect the current condition of a property.
Better Data for Assessors
The report also identified opportunities to improve the quality and quanitity of information available to Domestic Energy Assessors (DEAs).
While assessor error was found to have an average impact of around 6% on predicted heating demand, the effect could be significantly greater when important features such as dimensions, insulation or heating systems are recorded incorrectly.
To address this, the report recommends providing assessors with access to better supporting information, including historic EPC records, energy efficiency data and, where available, detailed SAP calculations for newer properties. These changes could help assessors produce more accurate assessments while reducing the likelihood of avoidable errors.
Refining the Assumptions Behind EPCs
Another area highlighted by the report relates to the assumptions used within EPC calculations. The research identified several areas where actual building performance differed slightly from modelled assumptions, including:
- Ventilation rates
- Heat loss calculations
- Solar gains
- Internal temperature modelling
- Electricity demand assumptions
The report recommends reviewing these assumptions as part of future model development. By incorporating more real-world evidence into the underlying calculations, future EPCs may provide a more accurate representation of how homes perform in practice.
Ongoing Validation Using Real-World Data
Perhaps one of the most interesting future improvements to EPCs identified by the report is the idea of continuous validation.
Historically, energy models have often been reviewed periodically. However, the report suggests that annual comparisons between modelled EPC outcomes and real-world smart meter data may now be feasible. This could allow emerging issues to be identified much more quickly and help ensure that future energy models remain aligned with how homes are actually being used. As technologies, heating systems and occupancy patterns continue to evolve, ongoing validation could play an important role in maintaining EPC accuracy over the long term.
The Growing Role of the Home Energy Model
Many of the report’s recommendations are closely linked to the development of the Home Energy Model (HEM).
HEM is being developed to replace SAP as the core methodology underpinning EPCs and other energy assessment applications. The EPC Accuracy Report was specifically commissioned to provide evidence that can help inform this transition. Rather than simply recreating the existing system, HEM presents an opportunity to incorporate lessons learned from decades of EPC data and real-world energy performance research.
Looking Ahead
The EPC Accuracy Report demonstrates that there is scope for future improvements to EPCs. From better use of building data and automatic updates following energy efficiency improvements, to refined modelling assumptions and the development of the Home Energy Model, the report outlines a range of opportunities to strengthen the EPC system.
These improvements could help ensure that EPCs continue to provide a reliable and useful measure of a property’s energy performance for homeowners, landlords, buyers and energy professionals alike.
High Quality Training
As the energy assessment and retrofit sector continues to evolve, high-quality training has never been more important. The knowledge and best practices that assessors develop at the start of their careers provide the foundation for producing accurate, reliable EPCs, whatever future changes may come to assessment methodologies. That’s why, at Energy Trust, we place such a strong emphasis on practical, engaging training delivered by experienced industry professionals. We want every learner to leave our courses with the confidence, skills and understanding needed to build a successful career and adapt to the changing demands of the industry.
Interested in becoming a Domestic Energy Assessor? Our Domestic Energy Assessor qualification provides the knowledge and practical skills needed to enter the energy assessment sector with confidence. For those already working in the industry, we also offer progression routes into specialist areas through our Retrofit Assessor course and the traditional buildings courses, helping you expand your expertise and career opportunities.
