The average EPC rating UK properties carry on their certificates may no longer reflect how those properties are actually performing, and England’s record wet winter of 2025 to 2026 is making that gap wider. After rainfall ran 42% above the long term average according to the Met Office, with some areas recording their wettest winter since 1836, millions of homes are operating at a lower effective thermal performance than their EPC certificate assumes. Understanding why this happens, and what it means for your property, is increasingly important as the 2030 compliance deadline approaches.
The Average EPC Rating by Property Type
Government EPC data for England and Wales shows that the average EPC rating UK existing dwellings hold sits around band D, specifically in the low to mid D range, corresponding to a score of approximately 60 to 65 on the 1 to 100 scale.
This average conceals significant variation. New builds (post 2010) predominantly rate at B or C. Government statistics for Q3 2025 show 85% of new dwellings received an A or B rating. Post war housing (1945 to 1980) typically rates at C or D depending on what improvements have been made. Pre 1919 solid wall properties rate at E, F or G in unimproved form, and these are precisely the properties most vulnerable to the moisture effects of a wet winter.
The average EPC rating UK landlords need to achieve by 2030 is C. The gap between where much of the housing stock currently sits and where it needs to be is significant, and wetter winters are quietly making that gap harder to close.
Why the Average EPC Rating by Property Type Can Overstate Real Performance
An EPC rating represents modelled energy performance, not measured energy use. A Domestic Energy Assessor visits the property, records specific features, wall construction, insulation presence, glazing type, heating system, and enters this data into SAP calculation software. The software outputs a score and band.
The EPC records what is theoretically present in the property. It does not measure how that fabric is performing. And it does not account for the condition of insulation, the moisture content of walls, or the effective thermal resistance of materials that have absorbed water.
Water is a much better conductor of heat than air. When insulation absorbs water, whether cavity fill mineral wool saturated by moisture bridging, floor insulation in a wet subfloor void, or loft insulation dampened by eaves defects, its effective thermal resistance drops significantly. Wet mineral wool can lose 50% or more of its dry thermal resistance. The insulation is still physically present. The average EPC rating UK calculation still records it as present. But it is not delivering the performance the certificate assumes.
What the SHDF Data Shows About Real EPC Improvements
The most useful published dataset on real EPC improvement comes from the Social Housing Decarbonisation Fund (SHDF). The government’s December 2025 SHDF statistics show that almost 100% of households upgraded under Wave 2.1, those starting from EPC band D or below, reached band C or above following the programme of works. Wave 2.2 replicated this result, with 99% of upgraded households reaching C or above.
This data demonstrates that moving properties well below the average EPC rating UK holds, E, F and G rated homes, up to band C is achievable at scale. However, it also reflects a package approach where multiple measures are installed together. A property that holds the average EPC rating UK properties sit at, band D, may need fewer measures but still requires accurate diagnosis of which measures deliver the most improvement.
Which Properties Are Most at Risk From Wet Winter Performance Degradation
Not all properties face equal risk from wetter winters degrading their effective thermal performance below the average EPC rating UK calculation assumes.
Properties with older cavity wall insulation. Mineral wool installed in the 1980s or 1990s that has settled or been exposed to previous moisture events carries greater risk of performance degradation in a wet winter than recently installed EPS bead systems.
Solid wall properties without EWI. Solid walls that have absorbed months of sustained rainfall are losing heat faster than their notional U values suggest.
Properties with suspended timber floors above poorly ventilated voids. Elevated void moisture means wet ground and potentially wet joist surfaces, both of which conduct heat more readily than dry equivalents.
Why This Spring Is the Right Time for a New EPC Assessment
Getting a new EPC assessment this spring serves two practical purposes for homeowners and landlords whose properties fall below or near the average EPC rating UK target of C.
First, it establishes an accurate current baseline under RdSAP 10, the updated methodology introduced in June 2025. Properties assessed before this date used the old RdSAP 9.94 methodology. Some property types, particularly solid brick properties with walls thicker than 280mm, may score differently under the new methodology.
Second, it triggers an up to date recommended improvements table. For landlords planning improvements to reach C before the 2030 deadline, an accurate 2026 baseline is more useful than a certificate issued several years ago before this winter’s rainfall tested the building fabric.
For detailed guidance on EPC bands, what the ratings mean, and how RdSAP 10 changed the methodology, read here
Frequently Asked Questions
What is the average EPC rating UK properties hold?
The average for existing dwellings in England and Wales is approximately D, in the range of 60 to 65 on the 100 point scale. New builds average B.
Does a wet winter automatically lower my EPC rating?
No. Your EPC certificate does not update based on weather conditions. However, your property’s real world thermal performance may fall below what the certificate assumes if insulation has been degraded by moisture this winter.
How can I tell if this winter has affected my insulation performance?
A thermal imaging survey of the internal walls in cold conditions reveals cold spots and areas of reduced insulation performance. A borescope inspection of the cavity can confirm whether cavity insulation is wet or degraded.
Should the average EPC rating UK holds be higher by now?
The average EPC rating UK properties hold has improved significantly over the past two decades through insulation programmes, glazing upgrades and heating improvements. However, the pace of improvement needs to accelerate to meet the government’s targets, and maintaining that improvement through increasingly wet winters requires resilient insulation materials and correctly specified systems.
Met Office climate projections available at metoffice.gov.uk