RDSAP10 effect on existing heat pump EPC rating?

AF1 · 2025-06-12T12:03:41Z

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

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Aaron

(@aaron)

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Joined: 11 months ago

Posts: 10

09/01/2026 8:07 pm

@mike-patrick If you’ve just invested circa 300k in a renovation, it’s very likely that detailed drawings, specifications and construction build-ups are available. From an energy consultancy point of view, that evidence can be used to carry out a full SAP assessment rather than relying on RdSAP. RdSAP is a reduced-data methodology and is heavily constrained by default assumptions on U-values, thermal bridging, airtightness and services efficiency, which means it often cannot credit high-quality fabric upgrades or well-designed building services in refurbished properties.

A full SAP assessment allows the dwelling to be modelled using measured or specified U-values, actual window and door performance, realistic air permeability figures, thermal bridge details and the true efficiency and control strategy of the heating and hot water systems. The result is a far more accurate calculation of heat loss and energy demand and, in most cases, a more representative (and often improved) EPC outcome compared to RdSAP. If you want a technically robust and accurate assessment based on how the building is actually constructed, give us a shout at EBSNI.com.

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Tim441

(@tim441)

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Joined: 3 years ago

Posts: 376

09/01/2026 8:37 pm

@mike-patrick interesting update - thanks.

I've been through an extended process on my EPC update.

Mine was done in 2020 pre ashp & solar/batteries

Updated recently to take into account changes. But i had not realised the criteria changes meant i had minuses as well as pluses

Latest criteria also mean glazing is more accurately measured for size and other detail. I have a lot of glazing - some single & some double

I was hugely disappointed that the heat pump was rated average & Hot water rated average. Both benefit from COP.

Anyway

Previous epc was D 67

Now D 62

In 2011 it was E 44

In 2015 before the modern extension it was D 55

At the end of day I've given up fighting further! It's all a nonsense.

With the improvements I've made i think the logical EPC would be mid C

Half house is modern build & insulation

Half is old, listed

Ashp, solar, batteries

Screenshot 20260109 201333 Samsung Internet

Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV

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