When comparing properties, it’s common to assume that two similar homes will have similar Energy Performance Certificate (EPC) ratings. Yet in reality, one home might score a B, while a nearly identical property sits at D. Understanding why this happens is key for homeowners, landlords, and buyers looking to improve efficiency, reduce bills, and comply with regulations.
Factors That Cause EPC Rating Differences
Even when homes look identical externally, EPC scores can vary due to several subtle factors:
1. Insulation Differences
Wall insulation: One home might have retrofitted cavity or solid wall insulation, while the other hasn’t.
Loft and floor insulation: Small differences, like extra loft insulation or insulated floors, can significantly affect heat retention.
2. Heating System Variations
Older boilers, inefficient electric heaters, or poorly maintained systems lower EPC ratings.
Homes with modern condensing boilers or renewable heating systems (heat pumps, biomass boilers) score higher.
3. Windows and Doors
Double or triple glazing vs single glazing dramatically affects heat loss.
Draught-proofing and sealed frames also contribute to higher efficiency.
4. Ventilation and Air Tightness
Homes with uncontrolled air leakage or poor ventilation lose heat quickly.
Small gaps around doors, skirting, and rooflines can lower the EPC score.
5. Energy Controls and Behavioural Factors
Programmable thermostats, thermostatic radiator valves, and zoning can improve calculated energy performance.
EPC methodology assumes typical usage patterns, but modern controls can still improve ratings.
6. Age and Construction Assumptions
EPC assessments rely on property age and building type for default U-values when documentation is missing.
Two “similar” homes built in the same era might have different retrofits or unrecorded improvements, leading to rating gaps.
Why EPCs Can Be Misleading
EPCs are estimates, not exact measurements.
Small differences in insulation, heating, or documentation can shift the score by several bands.
Assessors make assumptions if evidence of improvements isn’t available — one home may benefit simply because certificates or visible installations exist.
How to Minimise EPC Gaps
Keep detailed records of insulation, heating, and renewable upgrades.
Maintain and service your heating system regularly.
Upgrade windows, doors, and lofts if needed.
Consider a re-assessment if your property has had energy improvements since the last EPC.
Expert EPC Services with Urgent EPC
At Urgent EPC, we ensure accurate EPC ratings that reflect your property’s true efficiency. Our assessors carefully review insulation, heating systems, windows, and other energy-impacting factors to minimise rating discrepancies.
Explore our services:
Contact Us to book your EPC today.
Final Thoughts
Even two seemingly identical homes can have very different EPC scores due to subtle variations in insulation, heating, windows, and documentation. Understanding these factors helps homeowners make targeted improvements, comply with regulations, and increase property value.
