Heat pumps, it seems, are not as much hassle as they used to be. Anne and Neil Clark first inquired about installing one in the annexe of their Windermere home four years ago but quickly decided it would be too much faff. The installer told them they would have to swap out their old radiators for larger ones that could keep the building warm at a lower flow temperature.
So they decided to stick with the annexe’s old oil-fired boiler. “But it was really at the end of its life,” Neil says. “To keep it working we were having more callouts than the NHS.” So late last year they inquired about a heat pump again, and this time they were pleasantly surprised. The installer told them that the technology had improved so much that they would no longer have to swap out their radiators. Instead they could get a Mitsubishi Ecodan R290 — one of several high-temperature models that have recently come on the market.
Capable of heating water to 75C, it’s a far better fit with imperfect building fabric than lower-temperature models. Not only can it work with smaller radiators, but it’s also more likely to work with a smaller water cylinder because the speed at which it heats water means there’s less need to keep so much in reserve.
“It was important to us not to have to rip out the radiators, so the high-temperature model was a bit of a no-brainer,” Neil says. “It took a day to install and I was just amazed at how quickly the water came online. Normally, with a heat pump, you’d expect it to take a day or two to get going.”
They did have to get a new water cylinder to go with it because it was replacing a combi boiler. “But the cylinder went where the old heater was, it was dead easy to fit.”
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Thanks to the recent increase in the grant provided by the government’s Boiler Upgrade Scheme, from £5,000 to £7,500, Neil and Anne were able to knock £7,500 off the price of purchase and installation, leaving them with a bill of £893 — far less than the £4,000 they expected to pay for a new oil boiler.
The annexe has two flats. One is occupied by their son, Michael. The other, usually empty, they keep at 11C, “but if I want to use it then I just go in and switch the heating on and it doesn’t take long,” Anne says.
As they installed it only a month ago, they don’t yet have a clear idea of what its running cost will be across the year. But they do expect it to save them money because of how well it complements their 15-panel solar array and battery system. They used to spend £1,200 a year on oil. In contrast, in the summer months the electricity bill for their house and electric car is often only £30. “Air source heat pumps are good systems on their own,” Neil says, “but if you can add some solar it really is a no-brainer.”
High-temperature heat pumps aren’t a new concept. They’ve been around for decades, often used in hard-to-heat buildings such as churches. But for a long time they were the expensive, inefficient option. Older models achieved their higher temperatures by having an extra heat compressor — which meant that they were less efficient than lower-temperature models even when working at the same low temperatures. And at higher temperatures they were even less efficient.
In 2020, however, Vaillant brought out a heat pump with a new refrigerant — the R290 — that could achieve higher temperatures without a drastic drop-off in efficiency. Since then Mitsubishi, Samsung and Daikin have followed suit with their own R290 models.
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According to Adam Chapman, the founder of the heat pump installer network Heat Geek, this innovation is surplus to the requirements of most British homes, which do not need new radiators to stay warm at lower flow temperatures. But, he says, the new R290 models mean that those homeowners who would have had to replace their radiators will no longer have to, and installing a heat pump could save them money.
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“If you do a budget install of an R290 model,” Chapman says, “with no new radiators, no new water cylinder, it will cost less than a boiler change, and it will have comparable running costs to a boiler if installed correctly and controlled correctly, ie: not run up to 70C for two hours a day, more steady-state heating. You’ll save money from day one.”
Yet he adds that, over the longer term, homeowners would save more money if they invested in the building fabric changes that would allow the R290 models to work at a lower temperature: the insulation, and the larger radiators and water cylinder. “If you do that, you’ll break even around year ten, and over fifteen years it will save you more money.” This option would cost £5,000 to £10,000, factoring in the discount from the Boiler Upgrade Scheme.
Chapman advises homeowners to make sure that the high-temperature model they are being offered is an R290, not one of the older models that “low-quality installation companies” are still hawking.
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He says that R290 models have been “revolutionary” for his network of installers. “People have been arguing about the performance of heat pumps on the basis of old refrigerants that weren’t very good. The R290 model has now answered a lot of these concerns.
“They now work in hard-to-heat homes. They now heat all your hot water. You don’t need a back-up electrical heater like you did for the old refrigerants that didn’t get up to higher temperatures. All these arguments and moans about heat pumps have been answered with this new wave of high-temperature models.”
Is infrared heating a better option?
Of the many clean technologies that could replace the polluting gas boilers in our homes, heat pumps get by far the most attention. But Richard Hawkes, an architect who specialises in designing energy-efficient homes and a Homebuilding & Renovating Show expert, believes that another solution is being unduly neglected: infrared heating.
He recently installed this little-known technology in the Ewen Tree House, a designer eco-home nestled in the trees outside the Gloucestershire village of Ewen. Compared with the usual network of pipes and radiators, it’s marvellously simple. It consists of rolls of a thin, grey material called graphene-impregnated mesh skimmed into the ceiling. Once wired up and switched on, it begins to emit infrared rays.
Unlike radiators, which heat the air, these rays pass right through it to warm up surfaces directly, in the same manner as a space heater in a pub garden. But whereas space heaters can target particular spots with near-scorching heat, these rays aren’t as intense, and as they come from the entire ceiling they heat the room evenly. “It’s a gentle influence over a wide surface area,” Hawkes says. “It’s something you don’t notice being there.”
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Hawkes specialises in building homes in national parks that have to be adapted to their surroundings to get planning permission. He prefers to fit his houses with Energy Carbon’s infrared heating technology rather than a heat pump because it’s simpler and easier to maintain.
“With an air source heat pump you’d need a hot water tank, you’d need underfloor heating or radiators,” he says. “There’s annual maintenance, there’s the ten-year lifespan of the heat pump’s compressor.
“With an infrared system you don’t need underfloor heating or radiators, you don’t need the manifold unit, you don’t need such a large hot water tank to store the heat to distribute it. You don’t pay annual maintenance charges.”
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He adds that “it’s well suited to being installed within listed or old buildings, where installing a conventional central heating system may require damaging or interfering with existing historic building fabric”.
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Hawkes claims that it would cost “less than £10,000” to install Energy Carbon’s system in a typical three-bedroom house of 120 square metres. “I honestly don’t think you could get an underfloor heating system [for] that amount.”
Heat pump installations can cost up to £15,000, but thanks to the government’s Boiler Upgrade Scheme knocking £7,500 off that figure, they can in fact be cheaper than Energy Carbon’s system, and they don’t necessarily require underfloor heating. And unlike infrared, a heat pump will heat your water as well as your rooms. With an infrared heating system you would need a separate solution for hot water such as a Mixergy tank.
“If you’ve got a very large house that’s very hungry for heat, poorly insulated, then I’d say choosing something different would be better, possibly a heat pump, possibly a biomass boiler,” Hawkes says. “We design energy-efficient houses, so for us it’s going to be difficult for anything to beat infrared.”
For free tickets to the Homebuilding & Renovating Show at the NEC, Birmingham, on March 21-24, visit homebuildingshow.co.uk.
