Renewable Energy System Design & Development
Fix the planet with heat pumps
Hi, welcome to Fix the Planet. I wrote this dispatch in a cold room of our Victorian house, wearing two jumpers while wishing I had better insulation and a heating system that didn’t burn fossil fuel.
This week’s email is about a technology that could be the solution: heat pumps. Effectively a fridge in reverse, they use electricity to extract heat from the ground, air or even water. Most homes would use an air heat pump, which sits on the outside of a building and looks like an air conditioning unit.
Around 30,000 are being installed in UK homes each year, but yesterday the UK government’s advisers, the Climate Change Committee (CCC), said that needs to jump to a million a year by 2030. The advice came just days after the UK government set a target of 600,000 a year by 2028 . Officials also accidentally let slip that gas boilers will be banned in new homes from 2023, leaving a hole that, for the most part, only heat pumps can fill.
But how does a heat pump compare to a gas boiler? What changes might you have to make? How do we go from a tiny supply chain today to a million annual installations in a decade? Where will all the electricity to run them come from? And why not hydrogen boilers? Scroll on.
Infrared thermovision image showing lack of thermal insulation on House.
Photo: Shutterstock/Ivan Smuk
The slightly glib answer is they are here and they work. There are few green heating alternatives ready now. Low-carbon hydrogen supplies don’t exist beyond small-scale trials and hydrogen boilers aren’t a thing you can buy for your home yet. District heating, where heat is piped from a big central source in a town, is only suitable for about a fifth of UK homes, according to the CCC. Electric heating is inefficient. So that leaves heat pumps.
In the UK, anyone buying a new home after 2023 or anyone living in one of the roughly 15 per cent of homes off the gas grid, who are reliant on polluting and expensive options such as oil boilers. The CCC estimates those two groups will account for about 4 million of the 5 million heat pumps it expects in UK homes by 2030. “We will see a rapid increase in the uptake of heat pumps in the coming years. There’s no reason why they couldn’t become the de facto heating systems over the next decade or so,” says Greg Jackson at UK energy firm Octopus Energy.
A typical air source heat pump. Photo: Mitsubish Electric
“They do definitely cost more [than a gas boiler],” says Richard Lowes at the University of Exeter, UK – usually three times the cost of installing a gas boiler, he says. Running costs are roughly the same, because the cut in your gas bill is offset by your increased electricity consumption, and units of electricity cost more than gas. A big benefit is they tend to last longer than the 10-15 years of a gas boiler, says Lowes. Max Halliwell at Mitsubishi Electric, which makes heat pumps in the UK, says an air source one might typically cost about £7000 to £8000, though the price varies depending on the size of your home and how efficient it is. Most manufacturers making the machines have backgrounds in either air conditioning (like Mitsubishi), or gas boilers (like Germany’s Vaillant), so Halliwell thinks there isn’t much to gain from economies of scale. He reckons savings could come from the expansion of today’s small number of installers, to encompass more “one man and his band” plumbers. Some installers charge a premium because of the distance they have to travel to homes, for example. Halliwell thinks costs could come down 15 to 20 per cent over time.
Once you’ve got one, they tend to fade into the background. Getting one does require a more complex set of considerations than simply chucking in a new boiler. First, a home needs to be as efficient as possible, with insulation and draught-proofing. That’s because heat pumps work more effectively at lower “flow temperatures” – the temperature of water running through your radiators. You’ll also need a hot water tank or cylinder, something that has been removed in many UK homes as combi gas boilers have been fitted. “I think that’s one of the biggest consumer issues. But engineers are putting them in loft spaces and in eaves, and being smart about it,” says Lowes. Some homes may need new radiators, with double panel radiators, rather than single panel ones.
Once a heat pump is fitted, they generally run for longer periods at lower temperatures than a gas boiler. “It’s much better for the internal temperature, it doesn’t go up and down as much, which can help with condensation issues,” says Lowes. Two scare stories are that they are huge and noisy. Jan Rosenow at the Regulatory Assistance Project, a clean energy non-profit organisation, had one installed in his garden last year. The big motivation for him was carbon savings, but he has also blogged about a cut to his energy bills. Noise and size are non-issues, he says. “No one has complained. We haven’t heard it, noticed it,” he says, adding that his family are usually only in the garden during the summer when the pump isn’t operating, so noise hasn’t been a problem.
Octopus Energy has gathered data on 157 heat pump customers on its Agile tariff, which charges more for electricity at peak times and less off-peak. Check out the blue line on the graph above in the red shaded area and you can see some heat pump owners with the supplier are saving money by turning their heat pump down or off during peak times.
Even the CCC calls the supply chain “weak”. “The ramping up has got to be so quick. It’s such a huge transformation of the market,” says Lowes. Rosenow says history holds lessons of how hard it will be. An early scheme to get people to switch to cleaner heating systems, called the Renewable Heat Incentive, has a target of 520,000 installations between 2014 and 2022. So far it has only achieved about 80,000 installations . “That suggests to me that 600,000 heat pumps in 2028 is not easy,” says Rosenow.
Part of the challenge will be getting enough skilled people to fit them. “The key concerns are around supply chain skills. There just aren’t enough people out there to install them,” says Jenny Holland at the UK Green Building Council. Here’s an indication of scale: Mitsubishi Electric has around 1200 installers, and about a third of the UK heat pump market. On the flip side, the company says people can be trained quickly to install them. Jenny Hill at the CCC says getting from 30,000 to 1 million a year in a decade is doable, because the group consulted with industry on its uptake figures and found them “robust and feasible”.
The status quo. “I think the biggest obstacle is that gas boilers are cheap, easily available and have a good supply chain. They work well and people know them,” says Rosenow. He, Jackson and Holland think one answer is a “sin tax” on the price of gas, to reflect it now being more carbon intensive than electricity. Subsidies, such as the UK government’s recent extension of the Green Homes Grant for householders in England , will help, but won’t be enough alone, says Rosenow. There’s also the hassle factor of installations. One big risk is badly installed hardware tarnishing the image of heat pumps. “That can give technologies a bad name. That is a big risk for heat pumps, if there’s not enough attention being paid to quality installations,” says Rosenow.
Finally, the UK is going to need more clean electricity generation. Demand has been falling in recent years due to efficiency measures, but the CCC projects heat pumps combined with electric cars will drive it back up again. Check out the graph below for how the CCC thinks cumulative heat pump numbers in UK homes will grow. Energy networks will cope in the short term. “Because electricity demand has gone down there’s a lot of spare [power station] capacity,” says Lowes. Longer term, far more windfarms will be needed for capacity, and local wires will need “reinforcing”, with the costs borne by all energy billpayers.
Ditching gas boilers for heat pumps won’t be easy, but making it happen could show other countries the way forward, says Rosenow: “It’s a big challenge, but if the UK manages to do that, it’ll be world-leading.”