An Energy Performance Certificate (EPC) provides a snapshot of a property’s energy efficiency at the time of assessment. While homeowners often assume a high EPC rating is permanent, ratings can decline over time due to changes in the property, system efficiency, or EPC methodology. Understanding why this happens and how to prevent it is key to maintaining energy efficiency, compliance, and property value.
Our EPC Assessors in London frequently help property owners protect their ratings through targeted upgrades and maintenance:
👉 https://epcrate.co.uk/services-epc-assessors-london/
1. How EPC Ratings Are Calculated
EPCs assess energy efficiency based on:
Building fabric: walls, floors, roofs, insulation
Windows and doors: glazing type and draught-proofing
Heating systems: boilers, heat pumps, radiators
Heating controls: thermostats, TRVs, zoning
Lighting: fixed energy-efficient lighting
Renewable energy systems: solar PV, solar water heating, heat pumps
The rating assumes all elements are well-maintained and functional at the time of assessment.
👉 Learn more about EPC assessments:
https://epcrate.co.uk/about-us-epc-company-london/
2. Reasons EPC Ratings Can Drop Over Time
Several factors can reduce a property’s EPC rating:
a) Degradation of Building Fabric
Loft insulation can compress or shift
Cavity walls can become damp or settle
Draughts may develop around windows and doors
b) Aging Heating Systems
Boilers lose efficiency as they age
Heat pumps and radiators can underperform
Controls may malfunction or become outdated
c) Changes in Usage
Increased occupancy
Frequent heating or hot water use
Installation of non-efficient appliances
d) EPC Methodology Updates
Software and calculation methods are updated
Band thresholds may shift
Previously unaccounted factors (like thermal bridging) may be included
Even without physical changes, EPCs may drop due to updated assessment standards.
3. Preventing EPC Score Declines
Maintaining EPC performance requires regular monitoring and strategic upgrades.
a) Maintain Insulation and Draught-Proofing
Inspect loft and cavity insulation
Seal gaps around windows, doors, and floors
Repair damaged insulation
b) Service and Upgrade Heating Systems
Annual boiler or heat pump servicing
Replace aging systems with efficient models
Ensure heating controls are functional
c) Update Lighting
Replace old bulbs with fixed LED lighting
Ensure permanent fittings are energy-efficient
d) Implement Minor Upgrades
Add TRVs to radiators
Zone heating for multi-room properties
Check renewable energy systems for proper operation
Even small, cost-effective measures can prevent rating drops.
4. Timing EPC Re-Assessments
EPCs are valid for 10 years, but a re-assessment before expiry is often beneficial:
After completing efficiency improvements
If previous EPCs were inaccurate or outdated
To reflect upgraded systems and insulation
👉 Schedule a re-assessment:
https://epcrate.co.uk/booking/
5. The Financial Impact of a Dropping EPC
A lower EPC can have significant consequences:
Reduced property value: Buyers may discount energy-inefficient homes
Compliance issues for landlords: Minimum EPC standards must be met
Higher energy bills: Reduced efficiency increases running costs
Future-proofing risks: Low-rated properties may be harder to sell or refinance
Proactive maintenance and upgrades are cheaper than dealing with declines later.
6. Key Takeaways
EPC ratings are not permanent and can decline due to building wear, aging systems, usage changes, and methodology updates.
Regular maintenance of insulation, heating, lighting, and controls can prevent declines.
Strategic upgrades improve energy efficiency and protect property value.
Proper documentation is essential to ensure improvements are recognised during re-assessment.
Maintaining a strong EPC rating safeguards long-term property value, reduces energy costs, and ensures compliance.
.
