Your EPC rating isn’t fixed forever. Even if your property scored well a few years ago, changes in assessment methodology, building wear, and updated energy benchmarks can all cause your rating to shift — sometimes without any physical changes to the property itself.
This page explains why EPC ratings can change over time, what drives those changes, and what Oxfordshire landlords can do to stay ahead.
Why Would an EPC Rating Change?
There are several reasons your EPC score might differ from one assessment to the next:
- Methodology updates: The way EPCs are calculated has changed significantly. The shift from RdSAP 9 to RdSAP 10 introduced new assumptions about heating, insulation, and ventilation that can raise or lower scores.
- Building degradation: Ageing heating systems, deteriorating insulation, and worn seals all reduce energy efficiency over time.
- Fuel price and carbon factor changes: The underlying data that feeds into EPC calculations is periodically updated to reflect current energy costs and grid carbon intensity.
- Assessor interpretation: Minor differences in how assessors record building features — such as wall type, glazing age, or boiler condition — can influence the final score.
How RdSAP 10 Has Changed Scores
The introduction of RdSAP 10 in 2024 was one of the most significant updates to the EPC methodology in recent years. Some properties have seen their ratings improve, while others have dropped — even without any physical changes.
Key changes under RdSAP 10 include revised heating system efficiencies, updated thermal bridging assumptions, and new treatment of ventilation losses. For a detailed technical breakdown, visit our sister site’s AI EPC Property Hub.
What Does This Mean for Landlords?
If your current EPC was issued several years ago, the rating shown may no longer reflect how your property would score today. Under MEES regulations, landlords must ensure rental properties meet a minimum EPC rating of E. A property that previously scored an E could now fall to an F under the updated methodology.
This is particularly relevant if you are:
- Renewing a tenancy or entering a new lease
- Preparing a property for sale or re-let
- Planning energy improvements and want to know your current baseline
Should You Get a New EPC Before Yours Expires?
EPCs are valid for 10 years, but validity doesn’t mean accuracy. A certificate from 2015 was produced under a completely different methodology and energy landscape. Getting a fresh assessment gives you a clear picture of where your property stands today — and what improvements would have the most impact.
If your property is borderline, an early reassessment can help you identify problems before they become compliance issues.
How to Protect Your Rating
There are practical steps you can take to maintain or improve your EPC rating over time:
- Service your boiler annually and replace ageing heating systems before they drag down your score
- Top up loft insulation — it compresses and loses effectiveness over the years
- Upgrade to double or triple glazing where single glazing remains
- Consider smart heating controls, which are now factored into RdSAP 10 assessments
- Check draught-proofing around doors, windows, and loft hatches
For more detailed guidance on improvements, see our page on how to improve an EPC rating for a rental property.
Frequently Asked Questions
Can my EPC rating change without any work being done?
Yes. Changes to the assessment methodology, updated carbon factors, or different assessor interpretations can all result in a different score, even if the property itself hasn’t changed.
How often is the EPC methodology updated?
There is no fixed schedule, but major updates like the move from RdSAP 9 to RdSAP 10 happen periodically. Minor data updates to fuel costs and carbon factors can occur more frequently.
Is it worth getting a new EPC before mine expires?
If your EPC is more than a few years old and your property is close to the minimum rating, it is worth getting a fresh assessment to understand your current position.
Book an EPC Assessment
E8 Property Services provides EPC assessments across Oxfordshire. If you want to know where your property stands under the latest methodology, we can help.
Book an EPC assessment or call 01865 339535 to discuss your property.