An Energy Performance Certificate (EPC) provides a snapshot of your home’s energy efficiency at a specific point in time. Many homeowners assume that once a property achieves a high EPC rating, it will stay that way indefinitely. However, EPC ratings can decline over time, and understanding why this happens is key to maintaining energy efficiency and property value.

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1. How EPC Ratings Are Determined

EPC ratings are calculated using:

  • Building fabric: walls, floors, roofs, insulation

  • Windows and doors: glazing type and draught-proofing

  • Heating systems: boilers, heat pumps, and hot water systems

  • Heating controls: thermostats, TRVs, zoning

  • Lighting: fixed energy-efficient lighting

  • Renewable energy: solar panels, heat pumps

The rating reflects theoretical energy efficiency, assuming all components are properly maintained and functional.

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2. Why EPC Ratings Can Drop Over Time

Several factors can cause a decline in EPC scores:

a) Wear and Tear of Insulation and Building Fabric

  • Loft insulation can compress or shift

  • Cavity walls can become damp or settle

  • Draughts may develop around windows and doors

Even small changes in building fabric can reduce heat retention, lowering your EPC.

b) Aging Heating Systems

  • Boilers lose efficiency as they age

  • Heat pumps and radiators can underperform

  • Heating controls may become faulty or outdated

An older, inefficient heating system directly reduces calculated energy efficiency.

c) Inefficient Maintenance of Heating Controls

  • TRVs may stick or be removed

  • Programmable thermostats may fail or be misconfigured

  • Zoning systems may stop working

Faulty or missing controls are a common reason for EPC score drops.

d) Changes in Property Use

  • Increased occupancy

  • More frequent heating or hot water usage

  • Installation of non-efficient appliances

While EPCs assume standard use, actual changes in usage can reveal inefficiencies.

e) EPC Methodology Updates

  • EPC calculations and standards evolve

  • New software versions may assess previously unrecorded features

  • Band thresholds can shift, meaning an unchanged property may receive a lower score

This is why older EPCs can become “out of date” even without physical changes.

3. Preventing EPC Score Drops

Maintaining or improving your EPC rating requires regular monitoring and strategic upgrades.

a) Maintain Insulation and Seals

  • Check loft and cavity insulation regularly

  • Seal gaps around windows, doors, and floors

  • Repair damaged or degraded insulation

b) Service and Upgrade Heating Systems

  • Service boilers and heat pumps annually

  • Replace aging units with efficient models

  • Ensure heating controls are functional and correctly configured

c) Update Lighting

  • Replace old halogen or incandescent bulbs with LED lighting

  • Ensure permanent fittings are energy-efficient

d) Consider Minor Renovations

  • Install TRVs on all radiators

  • Implement zoning controls in multi-room properties

  • Check renewable systems for proper operation

Even small improvements can prevent drops or push a property into a higher band.

4. Timing Your EPC Re-Assessment

EPCs are valid for 10 years, but a re-assessment before the expiration can be beneficial if you have made improvements or maintenance upgrades.

  • Ensure all high-impact measures are completed

  • Gather certificates, invoices, and documentation

  • Schedule your assessment to reflect current energy efficiency

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5. Why Preventing a Drop Matters

A declining EPC can have serious consequences:

  • Lower property value: Buyers may discount homes with poor ratings

  • Compliance risk for landlords: Minimum EPC standards are mandatory

  • Higher energy bills: Less efficient homes cost more to heat and power

Preventive measures save money, maintain property value, and ensure regulatory compliance.

6. Key Takeaways

  • EPC ratings are not permanent; they can drop due to wear, aging systems, faulty controls, and methodology updates.

  • Regular maintenance of insulation, heating systems, controls, and lighting can prevent rating declines.

  • Strategic upgrades are the most cost-effective way to maintain or improve EPC scores.

  • Documentation is essential to ensure upgrades are recognised during re-assessment.

Maintaining a strong EPC rating is not just about compliance—it’s about protecting your property value, reducing energy costs, and ensuring comfort for occupants.

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