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The EPC Dilemma: How Current Ratings Fail Heat Pumps

Chris Flaherty · 2024-01-04T21:00:00Z

This article isn’t meant to criticise heat pumps; rather, it questions the effectiveness of the EPC system for energy ratings. In December 2023, I completed a comprehensive refurbishment of a flat, enhancing its layout and adding internal wall insulation (IWI) to all external solid walls, substantial loft insulation, underfloor insulation, and new double glazing. The plumbing overhaul included a new bathroom and kitchen. For the heating, I recommended an air source heat pump (ASHP) and underfloor heating (UFH) to the client, who was receptive to my advice given the system's energy efficiency. I installed a Vaillant UK aroTHERM plus with a Joule Heat Pump cylinder. The UFH system was designed by the manufacturer, tailored to the heat loss calculations of each room. For control, I chose Vaillant’s sensoCOMFORT and weather compensation control. Considering the compact size of the flat, I didn't install a buffer tank; the only pump used was the one integrated into the aroTHERM ASHP. I deemed individual room temperature control unnecessary for such a space and opted for a full weather-compensated control for the entire property. The system was well insulated both internally and externally, performed well, and heated the flat effectively with a flow temperature capped at 45C. When it came time to obtain an Energy Performance Certificate (EPC), I encountered the system's shortcomings. Despite the extensive upgrades, the walls, windows and roof received good ratings, but the ASHP and UFH were only deemed 'Average'. Moreover, the hot water system was rated 'Poor', and the weather compensated control was rated 'Average', possibly because it was categorised as a programmable room stat rather than a weather compensated control. This raises the question: What system would achieve a 'Good' or 'Very Good' rating if not an ASHP with UFH? The EPC rating is a significant factor in convincing homeowners to switch to heat pumps. Is this an issue with individual assessors, or is it the SAP calculations they must follow? In my view, the current EPC system is outdated and potentially detrimental to the heat pump industry. I’m curious to hear others' experiences with EPC ratings and their thoughts on its impact on the adoption of heat pumps. Editor's note The EPC is a vital tool for homeowners, offering a detailed overview of a property's energy efficiency and carbon emissions. This rating is not only crucial for understanding a home's energy performance but also influences property values and compliance with environmental standards. However, as Chris points out through his firsthand experience, there appears to be a discrepancy in how EPCs evaluate certain energy-efficient technologies. The case in question involves a comprehensive refurbishment of a flat, where various energy-saving measures were implemented, including the installation of an ASHP. Despite these sensible upgrades, the EPC assessment yielded unexpectedly average ratings for the ASHP and underfloor heating, and even a poor rating for the hot water system. This raises important questions about the current EPC system's ability to accurately reflect the efficiency and environmental benefits of ASHPs. Are these innovative heating systems being unfairly penalised by an outdated assessment methodology? If so, this could inadvertently discourage homeowners from adopting ASHPs, which are known for their energy efficiency and lower carbon footprint compared to traditional heating systems. Going forward, the SAP calculations must be revised to better account for the specific efficiency and performance characteristics of air source heat pumps, considering factors like weather compensation control, underfloor heating integration and system sizing.

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Toodles

(@toodles)

Illustrious Member Contributor

Joined: 3 years ago

Posts: 2064

24/09/2024 5:33 pm

@jancold Likewise, I had ours carried out for the purposes of the BUS grant . (Notionally a B now, but certified as a C before we carried out Solar PV and ASHP.)

https://find-energy-certificate.service.gov.uk/energy-certificate/0370-2739-3170-2622-2441

I can’t help feeling that ‘Lip Service’ is the most appropriate expression. Regards, Toodles.

This post was modified 12 months ago by Toodles

Toodles, he heats his home with cold draughts and cooks his food with magnets.

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rodwebster

(@rodwebster)

New Member Member

Joined: 6 months ago

Posts: 1

19/03/2025 7:04 pm

Hi, im not an expert on EPCs but today got a D for my 1930s detached with an ASHP. Fortunately, I installed a hybrid system which is also capable of heating the whole house by gas. So I asked the EPC guy to assume that the ASHP was derelict. I gained 10 points - high C!

I think the reason is that the heat pump is “charged” for the inefficiency of generating electricity (30%?) whereas boilers are very highly efficient. Of course, I am on Octopus, which claims to be 100% green.

I could be wrong but I think this might be the reason heat pumps are a bad thing from an EPC point of view.

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Judith

(@judith)

Prominent Member Member

Joined: 2 years ago

Posts: 381

20/03/2025 3:09 pm

The government has just closed a consultation on the principles of updating the EPC. See here https://www.gov.uk/government/consultations/reforms-to-the-energy-performance-of-buildings-regime/reforms-to-the-energy-performance-of-buildings-regime#overview-of-proposed-reforms

And will further consult on the details (as stated in the overview of above).

The are many established “sillinesses” in the EPC even it was done perfectly (rare).

Your comment on the use of primary fuel consumption is one such stupidity, since it assumes the UK electricity is generated mainly by coal and gas, which is no longer true.

One silly example is my in-laws have a wood burning stove which gives them extra points and A EPC on their 9 year old well- insulated house with a small area of solar panels. So when we had our EPC done (for ashp) our points came out as a B (see stuff below) despite being less well insulated, but they missed off our wood burning stove. So I pointed this out and they admitted their mistake but said that they would have to remove points for our wood burning stove because the rules had changed!

So eventually (after the next consultation) an ASHP will be a positive feature but the EPC is such a political (lobby-prone) tool that it barely performs as an energy performance certificate.

2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC

👍

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Mike Patrick

(@mike-patrick)

Honorable Member Member

Joined: 4 years ago

Posts: 172

20/03/2025 7:04 pm

I've commented earlier in this thread, finding the same problems with our EPC. Yes, its a known problem with the methodology and the government is taking far too long to address it. I'm an owner occupier but it produces another dilemma for landlords wanting to raise their EPC so that they remain legally able to let their properties. You can improve the EPC to get to a "C" rating or you can install a heat pump. But you can't do both!

Mike

Grant Aerona HPID10 10kWh ASHP

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