Good point... this slipped off my radar, and I've not really heard much about what to expect. 

Posted by: @af1

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Hi. RDSAP10 coming into force on 15th June 2025. Will EPC rating improve substantially for Heat Pump properties??   Maybe get from D to C?

RdSAP 10 represents a significant shift in how EPCs are calculated, particularly for properties with heat pumps. The revised methodology places greater emphasis on carbon emissions and gives more accurate credit to low-carbon technologies, smart heating controls, and integrated systems such as solar PV and battery storage. In theory, this should result in a notable uplift in EPC ratings for well-insulated homes with documented installations—potentially moving them from a D to a C rating. However, the practical reality is more complex. The accuracy of any EPC assessment under RdSAP 10 is heavily dependent on the quality of data input, which in turn relies on the availability of supporting evidence like installation certificates, specification sheets, and test results. Unfortunately, there is a persistent issue in the industry: many clients are reluctant to cover the cost of the additional time required for a comprehensive survey. As a result, assessors—working within limited budgets and tight timeframes—are often forced to rely on default values, which can significantly understate the true performance of the property. So while RdSAP 10 brings the potential for more accurate and favourable ratings, without proper engagement and investment from clients, much of that benefit risks being lost in practice.

@aaron Great response, thank you. Yes I already knew that Proof of all aspects is the key. I have everything regarding Glazing, GSHP, MVHR, EWI except the cavity fill certificate so I have emailed CIGA.  I had paid £300 for an SPF report for RHI.

On the lighter side, in this brilliant spoof, the legendary Ken Bone plays both the homeowner and the EPC inspector, capturing the absurd reality many UK homeowners face when renewables clash with outdated energy assessments. From heat pumps being ignored to solar panels dismissed as “ugly,” this tongue-in-cheek sketch shines a spotlight on how EPCs often miss the mark.

@editor  very good!! Im surprised he got the assessor into the property..

This is exactly why we don’t use RdSAP—it’s designed for speed and simplicity, not accuracy. We carry out all our assessments using full SAP software. It takes more time and effort, and yes, it does cost more—but the results are significantly more accurate and reflective of the building’s actual performance. When you're making decisions that affect long-term energy use and compliance, it's worth doing it properly.

@aaron What is the cost of a full SAP and will it bring the rating up in a property with GSHP, MVHR, DG, Full loft insu and 100mm Phenolic EWI?

@af1 prices will vary depending on size and complexity of the building.  Starting at around £300

@aaron will it bring the rating up in a property with GSHP, MVHR, DG, Full loft insu and 100mm Phenolic EWI?

@af1 if all of those features (GSHP, MVHR, double glazing, full loft insulation, and 100mm phenolic EWI) weren’t in place at the time of the last EPC, then yeah, you should see a significant jump in the rating when it’s reassessed.

@aaron All features were in place for the last several EPCs which were D rated. I need C.

An improvement to a C rating from D appears to hinge upon how the efficiency of the GSHP is arrived at. The report I paid for for RHI gave an SPF of 4.1 however I have been told the RDSAP COP figure is likely to be a farcical 1.7. The HP is MCS HP0016/08 - how can I obtain a COP or SCOP figure at 40C flow temp for SAP calcs?  There are those surveyors that say SPF and COP can be interchanged - is this true?  I have all the inputs that the SPF report used.