‘My house had the perfect energy rating – until I got a heat pump'

Telegraph

17-03-2025

Colin Ferguson's home may well be the ultimate net zero property – at least in theory.
The detached house in Perthshire, Scotland, was rebuilt from the ground up to be as energy efficient as possible. 'I completely redesigned it to near-Passivhaus standard,' he says, referring to an international efficiency standard for high performance buildings.
The renovation, for which Mr Ferguson, now 74, was involved in the labour, was completed in 2013. An energy assessor assigned a perfect efficiency score of 100, placing it in a band typically reserved for new builds. On the certificate, seen by The Telegraph, under suggested 'cost-effective improvements' it simply read: 'not applicable'.
Then Mr Ferguson installed a heat pump – and his perfect energy rating went up in smoke.
The retired insurance claims manager and his wife, Sue, had wanted to replace their oil-fired boiler with a heat pump, using £9,500 worth of government funding. This would require obtaining a new energy performance certificate (EPC) after the heat pump was installed, as their previous one was due to expire.
EPCs are at the heart of Labour's drive to net zero. Energy secretary Ed Miliband wants all rental homes to achieve a C rating by the end of the decade, forcing landlords to pay for costly upgrades or be banned from letting to tenants at all. Meanwhile, mortgage lenders are offering cheaper deals to homes with superior ratings – and punishing those with low EPC scores with higher rates.
But the certificates have been criticised in the past for their inconsistency. Assessors often rely on guesswork to work out a property's efficiency level, and some have been known to wrongly estimate a property's floor area by tens of square metres. Heat pumps, while greener, can often incur households higher bills. In some cases they have hurt rather than help a home's EPC score, as the certificates currently reward lower bills over carbon emissions.
'What really annoyed me was the little man who came in an Audi A8 to do the assessment,' Mr Ferguson recalls. 'In he waltzed. I had all the documentation from the original build – reams of stuff – and he took one look at it and said, 'I don't need any of that'. Had it not been for the fact we'd applied for a grant to put a heat pump in he'd have been out the door.'
Incredulously, Mr Ferguson's new EPC assessment had fallen to 74, placing it in the C band. The total floor area of the house also appeared to shrink between assessments – from 331 square metres to 279, the equivalent of three large bedrooms.
Dropping an EPC band can wipe thousands off a home's value in an instant, according to analysis by Knight Frank. The estate agent said moving from a D to a C could add 3pc value over and above local house price growth, equivalent to £9,000 based on average resale figures, while 80pc of buyers are said to be conscious of a home's energy rating when eyeing up a purchase.
It's not that Mr Ferguson's home has become less efficient, or less green, in the 10 years between assessments – far from it. The property makes use of solar feed-in tariffs, and as a result Mr Ferguson's home generates more energy than it consumes, turning his bill into a profit. Mr Ferguson's bills show the retiree spends about £1,300 a year on electricity for his home and electric car, which is entirely offset by the £2,000 he makes selling surplus power back to the Grid at times of high demand.
Mr Ferguson puts the change in his energy rating down to a shift in the way assessors grade properties. The first assessment made in 2013 used a standard assessment procedure (SAP), which tends to be done when a house is new. Any subsequent assessments are done with a reduced data SAP (rdSAP), which relies more heavily on assumptions.
The second assessment was carried out by Elmhurst Energy, Britain's largest EPC assessment firm. Despite the meagre score it assigned to Mr Ferguson's home, it suggests only one way he might improve it – by installing a wind turbine at a cost of between £15,000 and £25,000. Doing so, the document claims, would save him around £3,300 over three years and possibly bump up his score to 82, which barely scrapes a B.
Elmhurst Energy said the methodology of energy assessments had changed 'many times' since 2013, and now accounts for more up-to-date fuel prices, carbon emissions and other technologies used in modern homes such as battery storage and heating controls. The company added that since EPCs still reward low bills over carbon emissions, the green taxes applied to electricity mean switching to a heat pump disadvantages homes 'despite the fact they are better for the environment'.
To add insult to injury, the heat pump that Mr Ferguson had wanted in the first place does not work as well as he had hoped it would. The installers, Mr Ferguson says, were flummoxed by his unique home. Now, like several other heat pump owners, Mr Ferguson and his wife rely on a wood stove in the winter months to keep warm.
'To be fair to the chap, all these EPC companies use a particular system,' says Mr Ferguson. 'All they do is pump the information into some algorithm and it comes up with the certificate. The assessor just gets prompted with questions and puts in an answer, like a primary school kid ticking boxes.'
Stuart Fairlie, from Elmhurst Energy, which trains and accredits energy assessors who deliver more than one million EPCs annually, said: 'This shows an example of a homeowner who has done the right thing to reduce their home's carbon emissions by installing a heat pump, but the EPC rating has not improved.
'EPCs do change over time as the methodologies improve. Since 2013, they now account for new fuel prices, carbon emissions and low carbon technologies. The home's score is actually a good score for what is now a 12-year-old property, even though it may have been built above the minimum regulations at the time.
'We have been calling for the EPC to change for a long time. We expect the Government's reforms to make sure homes with low carbon heating systems are given the credit they are due on the EPC.'