Air to air heat pumps: the complete UK guide
In short
An air-to-air heat pump is the wall-mounted unit most people call air conditioning. It moves heat rather than generating it: outside to inside in winter, inside to outside in summer. One machine, both jobs.
In the UK it costs roughly £1,500 to £7,000 fitted depending on how many rooms you cover, and since April 2026 it has been eligible for a £2,500 Boiler Upgrade Scheme grant when it replaces your fossil fuel heating.
Check whether the £2,500 grant applies to your home. Takes about a minute.
Check eligibilityWhat an air-to-air heat pump actually is
If you have ever seen a slim white box on a bedroom wall with an outdoor unit on the wall outside, you have seen an air-to-air heat pump. In Britain we have called them air conditioners for forty years, which is why almost nobody realises they are heat pumps at all.
The machine has two parts. Outside, a condenser with a fan and a compressor. Inside, one or more fan units. Refrigerant circulates between them through a pair of copper pipes.
In summer the refrigerant absorbs heat from your room air and dumps it outside. In winter the cycle reverses: the refrigerant absorbs heat from the outdoor air, even at 2°C, and releases it into your room. It is the same physics as a fridge, pointed in whichever direction you need.
The important consequence is efficiency. A gas boiler burns fuel and can never exceed 100 per cent efficiency. A heat pump moves heat that already exists, so it routinely delivers three to four units of heat for every unit of electricity it consumes.
Air-to-air versus air-to-water
This is where most confusion, and most bad advice, comes from. The two technologies share a name and almost nothing else.
| Air-to-air | Air-to-water | |
|---|---|---|
| Delivers heat via | Fan units in each room | Radiators or underfloor heating |
| Provides cooling | Yes | No, in almost all cases |
| Provides hot water | No | Yes |
| Needs a hot water cylinder | No | Yes |
| Typical fitted cost | £1,500 to £7,000 | £8,000 to £18,000 |
| Boiler Upgrade Scheme grant | £2,500 | £7,500 |
| Install disruption | Low, no wet works | High, often new radiators and cylinder |
| Best suited to | Flats, smaller homes, homes that overheat | Family homes with an existing radiator circuit |
The single most consequential difference: an air-to-air system does not heat water. If you install one as your only heating, you still need a solution for hot water, typically an immersion cylinder or a separate hot water heat pump.
That is also why the grants differ. £7,500 for a system that replaces your whole heating and hot water setup, £2,500 for one that replaces space heating only. We cover why the grants are different and what happens to your hot water and your boiler in more detail.
How efficient are they, really?
Efficiency is measured as SCOP, the seasonal coefficient of performance: the average units of heat delivered per unit of electricity across a full heating season, tested to EN 14825.
Air-to-air systems typically return a SCOP of 3.0 to 4.0. A SCOP of 3.5 means three and a half units of heat for every unit of electricity.
Whether that beats gas depends entirely on the price ratio between electricity and gas, which moves every quarter. At the Ofgem price cap for 1 July to 30 September 2026, electricity is 26.11p per kWh and gas is 7.33p per kWh.
| System | Cost per kWh of heat delivered |
|---|---|
| Air-to-air at SCOP 3.5 | About 7.5p |
| Air-to-air at SCOP 3.0 | About 8.7p |
| Gas boiler at 92 per cent efficiency | About 8.0p |
Calculated from the Ofgem price cap for 1 July to 30 September 2026. Refreshed each quarter.
So at current prices a well-specified air-to-air system is marginally cheaper to run than gas, and a poorly specified one is marginally more expensive. The break-even SCOP at the moment is around 3.5, which is why the efficiency rating of the specific unit you buy is not a detail.
Three things move the answer in your favour: better insulation, a specialist electricity tariff, and dropping the gas standing charge of 29.04p a day when you disconnect entirely.
Air-to-air has one structural advantage over air-to-water on efficiency. It heats air directly rather than heating water and then heating air with it, so it avoids a conversion step and reaches temperature far faster. It has one structural disadvantage: heat is delivered where the fan units are, so rooms without a unit stay cold.
What they cost
| System | Rooms covered | Typical fitted cost |
|---|---|---|
| Single split | 1 | £1,500 to £3,000 |
| Two-room multi-split | 2 | £2,800 to £4,500 |
| Three or four room multi-split | 3 to 4 | £3,500 to £7,000 |
| Ducted | Whole home | £6,000 to £15,000+ |
As at July 2026. London and the South East typically run 20 to 30 per cent above these figures.
Our full air conditioning cost breakdown covers this room by room, including sizing, hidden costs and how to reduce what you pay.
For install and running cost side by side, including the grant netted off, see our air to air heat pump cost guide.
The £2,500 Boiler Upgrade Scheme grant
On 28 April 2026, the Boiler Upgrade Scheme (England and Wales) (Amendment) Regulations 2026 came into force. The amendment made air-to-air heat pumps eligible for a £2,500 grant, removed the requirement for a valid EPC, put MCS certification on a statutory footing, and extended the scheme to 2030.
To qualify, the property must be in England or Wales and owned by the applicant, though second homes and let properties both count. You must be replacing a fossil fuel system, meaning gas, oil or LPG, or direct electric heating. The existing boiler is removed, with no hybrid and no backup. The air-to-air system becomes the primary heating source, with an indoor unit in every occupied room. An MCS certified installer applies for the grant and deducts it from your invoice. One grant per property, residential only.
Not eligible: cooling-only installations, new builds, properties already on low-carbon heating, non-domestic premises, and Scotland and Northern Ireland, which run separate schemes.
A timing caveat you will not find on most sites. The regulations are in force but the certification infrastructure is not finished. As of mid-2026 there were no publicly listed MCS-certified air-to-air products, and without a listed product an installer cannot raise a compliant grant voucher. See where the grant actually stands right now for the current position.
Who an air-to-air system genuinely suits
Good fit: flats and smaller homes where a hot water cylinder and radiator upgrade is impractical; properties with no existing wet heating system, currently on storage heaters or direct electric; homes that overheat badly in summer, where the cooling is worth as much as the heating; open-plan layouts where two or three units genuinely cover the living space; and anyone who wants low-disruption installation, typically one to two days with no plumbing.
Poor fit: larger family homes with many small rooms, where you would need a unit in every one; households who want a single system for heating and hot water; listed buildings and conservation areas where external units face planning resistance; and anyone whose priority is maximum grant value, where air-to-water at £7,500 is the better economics if the property suits it.
Noise, appearance and planning
Modern indoor units run at roughly 19 to 25 dB on low, which is quieter than a fridge. Outdoor condensers are the consideration, typically 45 to 55 dB at one metre, comparable to normal conversation. Siting matters more than the decibel figure: a condenser under a neighbour's bedroom window is a problem no specification solves.
On planning, many domestic installations fall under permitted development, but the exceptions catch a lot of people: conservation areas, listed buildings, flats and maisonettes, front elevations facing a highway, and local noise conditions. See our guide to planning permission for air conditioning.
Brands worth knowing
The UK domestic market is dominated by Japanese manufacturers. Mitsubishi Electric and Daikin sit at the premium end, typically 15 to 25 per cent above Toshiba, LG or Samsung at equivalent output. Panasonic sits in between.
Judge on three numbers, not the badge: rated output in kW for the room, SCOP for running cost, and indoor sound level in dB for bedrooms. If you intend to claim the grant, the fourth number matters most: whether the specific model appears on the MCS Product Directory.
How to get started
Work out which rooms you actually want covered, and whether this is a heating replacement or a cooling addition. That single answer determines whether the grant is available to you.
Check the planning position for your property type and area, then get three quotes from F-Gas certified installers, and MCS certified if you want the grant. Compare on SCOP and total scope of works, not headline price.
For what happens on the day, how long it takes and the certifications to ask for, read our guide to air to air heat pump installation.
Five questions to find out whether the government will pay £2,500 towards your system.
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