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.
Its installed price depends on the system design and property. Since April 2026 it has been eligible for a £2,500 Boiler Upgrade Scheme grant when it replaces qualifying fossil-fuel or non-heat-pump electric 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 |
| Hot-water provision | Depends on system design | Yes |
| Needs a hot water cylinder | Depends on system design | Yes |
| Installed price | Depends on design and property | Depends on design and property |
| 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 |
Most air-to-air systems deliver heat to rooms rather than water. Some system designs can contribute to domestic hot water, so an installer must confirm how the proposed installation will meet the property's full space-heating and hot-water needs.
Grant values depend on the eligible technology and the property's circumstances. 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.
Ask the installer for the selected product's published seasonal performance and a design for the specific property. Performance is not a reliable running-cost or savings prediction by itself.
At the Ofgem price cap for 1 July to 30 September 2026, the average Direct Debit unit rates are 26.11p per kWh for electricity and 7.33p per kWh for gas. Actual rates depend on tariff, payment method and region.
Price-cap figures are current for 1 July to 30 September 2026 and are not a personalised running-cost or savings estimate.
Running cost depends on the actual product, heat loss, controls, room coverage, tariff and usage. Compare those factors before relying on a saving claim.
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 | Quote scope to confirm |
|---|---|---|
| Single split | 1 | Model, refrigerant work, drainage and electrics |
| Multi-split | Multiple | Room coverage, capacity and pipework routing |
| Whole-home design | All required rooms | Heating design, hot-water provision and access work |
CoolGrant does not publish a national fitted-price range because it cannot establish the cost of a specific installation.
Our full air conditioning cost breakdown explains the scope to confirm in an itemised quote.
For factors that affect installed and running costs, 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 qualifying fossil-fuel heating, such as gas, oil or LPG, or non-heat-pump electric heating. A fossil-fuel heat-generating appliance cannot remain as part of the new heating system, and a hybrid system is not eligible. The heat pump must be capable of meeting the property's full space-heating demand, and the combined system must be capable of meeting its full space-heating and hot-water needs. 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.
Ofgem's Product Eligibility List, updated 23 July 2026, includes air-to-air heat-pump models. The list is an administrative aid rather than an eligibility decision: an installer must still confirm the model, property and installation meet all current BUS requirements. 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
Compare the model proposed for your property, not general brand rankings. Ask for its stated capacity, published seasonal performance, indoor sound level, warranty and installation scope.
If you intend to claim the grant, confirm that the installer can show the specific model is eligible and that the product, property and installation meet the current BUS requirements.
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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