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Heat pumps: have a cosy home without warming the planet

Patrick Collinson
·7-min read
<span>Photograph: Daisy-Daisy/Alamy</span>
Photograph: Daisy-Daisy/Alamy

When Graham Davidson and his wife, Pauline, retired to a bungalow in Norfolk three years ago they ripped out the old boiler and replaced it with an air source heat pump at a cost of £10,000. But this pricey replacement has turned into a moneyspinner for the Davidsons – and millions of British households are likely to follow suit in what is expected to be a revolution in home heating.

Davidson, 68, who used to work in the car electronics business, says it was financial gain rather than saving the planet that was at the forefront of his decision. But dumping the gas boiler has probably cut his household carbon emissions by more than half.

The couple took advantage of the government’s renewable heat incentive scheme, which will be worth a total of £7,000 to the Davidsons in quarterly payments over seven years. On top of that, they say their total home energy bills have fallen by up to £1,000 a year. Given that a new gas boiler would have cost about £3,000, the Davidsons reckon they will eventually save thousands of pounds.

Last week the government set a target of 600,000 heat pump installations a year in the UK by 2028 as it launched its “green industrial revolution”. It told housebuilders that in only three years’ time they will be forbidden from installing gas boilers in new homes and will have to put in a heat pump instead.

The pumps are electrical devices that work like an air conditioning unit in reverse

This is an extraordinarily fast-paced change; last year of the 1.6m boilers installed in the UK, only about 25,000 were heat pumps and the rest were traditional gas units.

The pumps are electrical devices that work like an air conditioning unit in reverse, sucking warmth out of the air or the ground outside and pumping it into your home via the radiators, without emitting harmful gases.

Existing householders won’t be forced to replace their old gas boilers – but if yours is reaching the end of its natural life, the experts say you should be seriously considering a heat pump while the very attractive government financial incentives remain in place.

However, there is also a backlash against these heat pumps, with critics saying they cost four times as much as a traditional gas boiler, require enormous taxpayer-funded subsidies – and even then won’t heat our homes as efficiently.

How much do they cost?

An air source heat pump.
The government has set a target of 600,000 heat pump installations a year in the UK by 2028. Photograph: KBImages/Alamy

There are two types – ground source or air source pumps. To retrofit an existing home with a ground pump requires extensive digging and will cost upwards of £20,000-£25,000, which makes them prohibitively expensive (and disruptive) for the majority of existing homes.

The air pumps – mostly made by Japanese air conditioner manufacturers such as Daikin and Mitsubishi – cost about £4,000 to £6,000 for the unit (two to three times the cost of a gas boiler), and then several thousand pounds more to install. What’s more, you may need to replace your radiators, which will push up the price even more, and then probably pay for a new tank as well.

Igloo Energy, which installed the Davidson’s unit, says their typical customer has a larger four or five-bed detached house and the average cost comes in at about £15,000, with new radiators and tank included. But they say the renewable heat incentive can knock about £11,000-£12,000 off that bill.

The government has also introduced the green homes grant, worth up to £5,000 against installation of a new pump, or £10,000 if you are on a low income.

Will they really heat up my house?

Yes, but not in the same way. Most air source heat pumps will only heat a standard radiator to 40-45C, compared with the 60-80C that a gas boiler achieves. So householders will generally need larger radiators to produce the same heat levels or turn existing single radiators into double radiators – and leave them on for longer. Heat pumps also can’t fire up the heat in your home at the same speed as a gas boiler.

After three years of using a heat pump, Davidson says: “You definitely need larger radiators but I really prefer it. OK, the heat’s not instant but I just don’t turn it off now, leaving the thermostat at 19C or 22C. We save around £1,000 a year, it’s never broken down and when we move I’ll definitely be installing another one.”

A common myth is that heat pumps won’t work in very cold weather but the industry points to the Nordic countries, which suffer more severe winters, and where heat pumps are far more common than in the UK. What does happen is that the compressor in the unit has to work harder, and therefore use more electricity, during cold snaps.

IMS Heat Pumps is an installer based in Perth, Scotland, and Sheffield in England. Its founder, Emma Bohan, says: “We do loads of work in Scotland. They work perfectly well at providing an ambient temperature all year round. You just have to make sure it is designed properly from the outset.”

Will I really save loads from my home heating bill?

The Davidsons’ savings are a bit of an outlier – in reality, most existing homes on the national gas grid will shave only a small amount off their energy bills. The financial equation in favour of heat pumps relies almost entirely on the RHI and the new green homes grant. Only if your existing system is oil-fired are you likely to make significant yearly savings by switching. You will also be expected to pay for an annual service (at about £100-£140) in the same way as gas boilers. But the installers say that breakdowns are far less common than in gas boilers and that heat pumps should last at least 15 years.

Are they bulky, ugly and noisy?

“They can be quite big,” admits Matt Clemow of Igloo Energy, “but there are some interesting looking new covers. And because they are put outside they will free up space inside your house where your current boiler is. They quietly hum. It’s like the noise you might hear standing about three metres away from a microwave when it’s on.”

Will they get cheaper? Will the grants disappear?

An air source heat pump.
Installers say breakdowns are less common in heat pumps than in gas boilers. Photograph: David McGill/Alamy

Unlike solar PV cells, which collapsed in price as global production soared, it is less likely these heat pumps will suddenly fall to the price of a conventional gas boiler any time soon.

Iain Bevan of the manufacturers Daikin says: “The prices have come down slightly and they will continue to come down but they won’t reach the level of a gas boiler. The main driver will be falls in the cost of installation as demand rises and the installer base grows.”

The grants and incentives therefore remain crucial for now. The government last week promised an additional £1bn to the existing £2bn available under the green homes deal but if there is mass take-up the money will soon run out.

Do they work in flats?

Maybe for a ground-floor flat in a converted house. But in general, flat dwellers will have to rely on communal heating systems as a better solution than individual gas boilers.

Are there any environmental concerns about the pumps?

Heat pumps have huge energy efficiency advantages over gas boilers. But like air conditioning units, they do contain hydrofluorocarbon refrigerants. Early ones (now banned) were blamed for helping destroy the ozone layer. The industry has moved to a new refrigerant, R32, with zero ozone-depleting potential and what manufacturers say is a “low global warming potential”.

Which pump should I go for?

The market is currently dominated by Daikin and Mitsubishi but the boiler makers Vaillant and Baxi are bringing out their versions and more will join. With so few installed, you can’t really ask your neighbour if their one was good value. This will be a market for consumer groups such as Which? to tackle over the next few years.

Sadly, none are made in the UK. Daikin makes units for the UK at its factory in Belgium and says if demand expands sufficiently it may consider production in the UK.