Home retrofitting: lessons and answers from heat pump geeks

But Mr Hackett, a former electrical engineer, driven by a “passion for the environment”, was keen to make his home into a kind of experiment. “People,” he said, “are waiting for solutions. That was a reason for doing it.”

He is one of a breed of DIY retrofit pioneers. There are around 40,000 heat pumps installed in Scotland, and about 250,000 across the UK, and they can be found in a variety of homes, from social housing to those of early adopter heat pump geeks. 

According to the Climate Change Committee, to reach our, now dropped, Net Zero 2030 targets,  Scotland should be installing 80,000 per year by the end of the decade. But most people have, as the innovation think tank, Nesta, put it to me “never seen one”.

Mr Hackett’s home is one I came across through a search through Nesta's Visit a Heat Pump scheme. Its website allows the heat-pump-curious to find a local host and go on a tour of a home. The result is something like a cross between a house viewing, and, in the hands of Mr Hackett, a practical science demonstration.

The cottage's roof is plated with a tesselation of 10 solar panels, and, inside, is home to a battery, and a smart electric shower. This, it turned out, is Mr Hackett’s unconventional approach to heating water - ditch the tank and install a German shower to supply all the hot taps in the house.

His bills, he noted, are now less than they were when he was on gas. "This month I'm going to have my first negative bill. Yesterday, on a sunny day, I was £3.50 in profit."

But, importantly, he has slashed his energy usage. “We used to use 12,000 units of gas per year. That’s down to just over 2000 units of electricity. - a huge cut,” he said.

Since he uses smart tariffs through the energy provider, Octopus, who invest their profits in green energy, that electricity is greener. But also, he said, the energy he uses from the grid between 4pm and 7pm is “almost zero”. This matters to him because one of his interests is how his battery storage and energy use can play a part in helping a future grid work at times of peak demand. "I want," he said, "to work with the grid and give back to it at those times."

The general advice on heat pumps is that they work best in well-insulated homes. But the question as Mr Hackett pointed out, is how far you take it? For an old cottage like his, the cost of the energy efficiency measures alone can be enormous.

“If you go for exterior wall insulation and interior wall insulation," he said, "it costs more than a heat pump. So I went for low-lying fruit. Draught-proofing of the doors and windows; loft insulation. These are things that aren’t too expensive..”

Pat Hackett with his heat pump

“Next is the heat pump, which can increase your coefficient of performance [heat produced per unit of energy used]. If you do all the insulation on a modern house, you can get that heat pump performance up to 4- 500%. In other words for every unit of electricity you’re consuming, you’re getting 4-500 units of heat. We get just over 300 %.”

Among the alterations that often comes with a heat pump, to make the system efficient, is the installation of large radiators - a process that, especially if combined with new piping, can be quite disruptive. But Mr Hackett chose only to replace two of his original radiators. 

One of the things, Mr Hackett often recommends to visitors to his heat pump tour is that they place their hands on the radiators. “They get a surprise when they touch the radiator, because it’s cool and they’ll sometimes say, it’s off? But I’ll say you’re 37C and it’s cooler than that, so it feels cool or warmish. But it’s actually warm.”

• READ MORE: Heat pump Scotland. Maps, graphs and missing targets
• READ MORE: Beyond the heat pump myths. From cost to that cold question
• READ MORE: How noisy are heat pumps? We put them to a sound meter test
• Heat pumps: Myths, truths and costs – find all articles here

He was keen to emphasise that living with a heat pump requires a shift in appreciation of the experience of heat and warmth we associate with the fire blazing in the hearth. The system works best when heated  "low and slow", allowing the walls and furniture to keep pace with the air temperature.

“It’s not like getting a fire and chopping the wood. With the heat pump, it’s the smart stuff, the controls, getting the right tariffs, the battery storage - that’s where it is all happening.”

Mr Hackett is on the Octopus Intelligent Flux tariff and can check his battery charge and usage through an app on his phone. He could be regarded as one of a new breed of heat pump geeks.  These are the tech lovers who like to tweak at their systems, share their data on the website heat pump monitor, or browse the coefficents of performance, tariffs, monthly electricity usage of others on that same site.

Pat Hackett checking his battery charge from his phone

Some, like Alistair McKay in Falkirk, who has the full decarbonisation panoply of an EV, air source heat pump, solar panels and a battery, revel in their home electrification experiment.

“I’ve always been fascinated by technology and sustainability," he said. "So when I bought my house two years ago, I knew that my first priority was kitting it out with as much technology and ideally sustainable technology as I could.”

Mr McKay,  who lives on his own in a two-bedroom semi-detached home built in 2016, also  has a Vaillant,  and uses Octopus as his electricity supplier, having shifted from initially using Intelligent Octopus tariff to its Agile tariff, through which he can control charging of his battery every half hour.

“At 4pm every day," he said, "the power rates for the next 24 hours get released and what I do then is check the solar prediction for the next day and based on how much sun there is going to be, I tell the battery when to charge. “

“Maybe it takes 20 minutes worth of thought a day, but I really enjoy it. I’m such an energy nerd. I never thought I would obsess over each kW that comes from my meter. On my desk in front of me, I’ve got my little in home display from my smart meter which keeps me up to date. It does pay off because my average unit cost last month was 8p.” (The average default tariff, since the recent price cap is 24.5p.)

But cheapness is not his key goal. “For me, it’s less cheapness and emissions, and more tech and emissions. I love my tech."

But not all early adopters regard the installation and running of a heat pump as a fun hobby. There are those, like Visit a Heat Pump host Paul Eastwood, an energy sector worker living in Victorian terrace home in Cathcart, Glasgow, who simply want to get the system fitted and have it run without too much tweaking. For him, it was mostly about getting off gas and reducing emissions. 

Far from wanting to experiment too much himself, when Mr Eastwood fixed on the idea of getting a heat pump, he was keen to find trustworthy advice and turned to the Glasgow cooperative  Loco Home Retrofit. “Making that shift is quite a big one and it can be difficult to navigate. It can feel a bit like the Wild West. Which is why independent assessment is so empowering in providing essential knowledge to engage with installers.”

The end result, as we found on a tour of the back garden of his 125-year-old home, is a Steibel Eltron, which ran with little more than a breeze of a sound when he switched it on. His home, however, he said, is "not massively insulated".

"We had some insulation put into the loft. There’s no underfloor insulation. There’s no wall insulation.  And the double glazing is fairly modest." Despite this lack, he said the house was extremely comfortable with bills "very likely lower" than when he was on gas. 

Not all of my heat pump owners were found through Visit a Heat Pump. Neil Kitching, author of the book Carbon Choices, writes a blog I have been following for some time which details his adventures in low carbon life, the electrification of his home and solutions to climate change.   

The book, he said, was inspired by the feeling, “the planet’s dying and nobody is doing anything about it; if people understood what was happening they might do something about it.”

Neil Kitching with his heat pump outside his Dunblane home   

Mr Kitching, whose Vaillant heat pump is tucked against a back wall, where it spills cool air over his tulips, believes he was either the first or second home to disconnect from the gas grid and get a heat pump in Dunblane.  He also has solar panels and the three 5kWh batteries, and an electric car, which, in the summer months is partially charged off the solar panels, and in winter is charged overnight from cheap electricity. 

He spent £14,000 for the heat pump and got a £7500 grant back [from Home Energy scotland]. The battery was £7000, £6000 of which was bought using an interest-free loan paid back over 12 years. He also got underfloor insulation, which he described as "tricky but worthwhile".  

Overall, he said his energy costs have gone down by one-third - though only because he has solar panels and battery. “If you just took out your gas and put in a heat pump, then you won’t be any better off because, while the heat pump has a 350% performance,  electricity is four times the price of gas. So it’s only by having the solar and the battery and charging it overnight that my costs are going down. The whole problem is the high price of electricity compared to gas." 

Not that saving money is what he is about. Mr Kitching is doing it for the planet and is pleased to say that the heat pump and its associated systems have cut his carbon footprint by two tonnes per year. It is, he said, one of the biggest things we can all do to slash our emissions. 

It's also something he believes is more accessible than is often made out.  “You get people saying, ‘Oh you’re middle class. You can obviously afford to do that.’”. “But if you are on benefits you might be eligible for free energy efficiency and a heat pump from the Scottish Government’s Warmer Homes Scotland scheme.   “And for the rest of us, if heat pumps were rolled out properly, with some government support, we could have lower bills. Same with electric cars. The batteries are improving all the time, costs are coming down too.  The future is electric.”