Air-to-Air Heat Pumps UK 2026: Costs, the £2,500 Grant and Who They Suit

What an Air-to-Air Heat Pump Actually Is

There's an outdoor unit, much like any heat pump's, and one or more indoor units, usually mounted high on the wall. Refrigerant pipes run between them and the indoor unit blows warm air into the room. If you've stayed in a hotel abroad with a wall-mounted air conditioner, that's the same thing: most of them heat as well as cool.

The difference from the heat pumps most UK guides talk about is what the heat goes into. An air-to-water heat pump heats water for radiators and a hot water cylinder. An air-to-air one heats the air in the room, so you don't need radiators or pipework full of water at all. That's why it's cheap, and it's also why it can't do your hot water.

There are a couple of less common types too. Some "all in one" units have no outdoor box, just two holes about 15 to 20cm across through the wall, which helps where you can't fix anything outside. And ducted systems hide the pipes in the ceiling, but they suit very efficient new houses more than the average British home.

The £2,500 Grant: What the Rules Say, and the Catch

The Boiler Upgrade Scheme has paid £2,500 towards an air-to-air heat pump since 28 April 2026. gov.uk lists it alongside the £7,500 for air-to-water and ground source. The rules, from gov.uk and Ofgem's installer guidance (version 5.1, July 2026):

• England and Wales only, and you must own the property (it can be a second home or one you let out)
• Residential properties only. The other heat pump grants can go to small businesses; this one can't
• You must be replacing fossil fuel heating, which gov.uk defines as oil, gas, electric or LPG, so electric heaters and storage heaters count
• The heat pump has to be able to meet the home's full space heating demand on its own. Hot water can come from something else, like an immersion heater, as long as it isn't fossil fuel
• One grant per property, so you can't have £2,500 for air-to-air and £7,500 for air-to-water on the same home
• It must be installed by an MCS certified installer, and the voucher lasts three months once it's issued
• Not for most new builds or social housing

In Scotland there's no air-to-air grant at all. The Boiler Upgrade Scheme doesn't cover Scotland, and Home Energy Scotland's own grant and loan list says air-to-air heat pumps are not eligible: it only funds heat pumps that provide all of a home's heating and hot water.

Now the catch. DESNZ's own Boiler Upgrade Scheme statistics show 145 air-to-air voucher applications and zero vouchers issued between 28 April and the end of August 2026, against nearly 123,000 issued for air-to-water heat pumps since the scheme began. The reason is certification. MCS said in April 2026 that its certification bodies were still getting UKAS accreditation to certify air-to-air installers, that each installer needs a technical supervisor qualified to Level 3 in refrigeration, air conditioning and heat pumps, and that products were still being added to its directory. Until an installer is MCS certified for air-to-air specifically, they can't claim the grant for you.

So treat the £2,500 as real but not yet reliable. Ask any installer, in writing, whether they're MCS certified for air-to-air heat pumps (not just air-to-water), and whether the product they're quoting is on the MCS product directory. If either answer is no, price the job without the grant.

What It Costs

Costs: Energy Saving Trust, "Air-to-air heat pumps", updated 11 September 2026. DESNZ doesn't publish air-to-air costs yet because there are too few installs. Redecorating around the indoor units and pipe runs is extra.

Compare that with an air-to-water heat pump: a median of £12,908 before its £7,500 grant in April to June 2026, so around £5,400 after it. Air-to-air is roughly a quarter of the price, and that's the whole appeal.

What It Costs to Run

The number that matters is what a kWh of heat costs. At the October to December 2026 price cap, with electricity at 26.32p:

SCOP is the bottom of each heating energy label band in the air conditioner labelling regulation (626/2011, Annex II, as retained in UK law), for the "average" heating season. Real-world performance in a cold snap is lower, and the Energy Saving Trust notes there's still little UK data on how these systems perform.

Against electric heating, that's the same warmth for around a fifth of the cost. Against gas, an A++ unit is about a third cheaper per kWh of heat, but because you'd still need a way to heat water, the case against a working gas boiler is weaker. Storage heaters on a cheap night rate sit in between, so put your own night rate into the calculator above.

Air-to-Air or Air-to-Water?

Who Should Get One

• Flats and small homes heated by electric heaters or storage heaters. This is the sweet spot: no radiators to fit, a small outdoor unit, and the biggest saving of any heat pump install.
• Homes with no wet central heating, where fitting radiators and pipework for an air-to-water system would cost thousands on top.
• Rooms that overheat in summer, like loft conversions. You get cooling for nothing, though fix shading and ventilation first.

Who Shouldn't

• A house with a working gas boiler and radiators. You'd still need the boiler or an immersion for hot water, and an air-to-water heat pump with the £7,500 grant does both jobs.
• Anyone who hates fan noise. The Energy Saving Trust notes indoor units can be noisier than other heat pumps. Ask to hear one running before you buy.
• Anyone buying on the grant alone. Until your installer is MCS certified for air-to-air, there is no grant.

What You Don't Need

A portable air conditioner is not an air-to-air heat pump. Most portable units are single-duct cooling machines; the ones that heat do it less efficiently than a fixed system, and none of them qualify for the grant. If you only want summer cooling for one room, see our portable air conditioner guide. If you want cheap heating, it's a fixed system you need.

Hot Water Without a Boiler

Most air-to-air units don't heat water, so you'll need one of these:

• A hot water cylinder with an electric immersion heater. Simple, and if you're on a cheap overnight tariff you can heat it in the cheap hours.
• An electric shower or small point-of-use water heaters at the taps.
• A hot water heat pump cylinder, which is a heat pump built into the cylinder, much cheaper to run than an immersion.
• Solar water heating or solar panels with a diverter feeding the immersion, if you've the roof for it.

Do You Need Planning Permission?

Usually not, in England. Since 29 May 2025 the permitted development rules for air source heat pumps (Class G of Part 14 of the General Permitted Development Order) cover any unit that "is not solely used for the purpose of cooling", so a heat pump you use for heating counts. The main conditions:

• Noise: it must pass the MCS 020 a) calculation, 37.0 dB(A) or lower at a neighbour's habitable-room window or door. Check your spot with our noise checker.
• Size: the outdoor unit can be up to 1.5 cubic metres on a house, but only 0.6 on a block of flats.
• How many: one on a semi, terrace or block of flats, two on a detached house. In a block of flats that means only the first one goes in under permitted development, so if a neighbour already has one, you'll need planning permission.
• Listed buildings and some conservation areas have extra restrictions.

If you own a leasehold flat, you'll usually also need the freeholder's permission to fix anything to the outside of the building, so ask before you get quotes.