Glossary · Heat pumps, grants and regulations
What is an air to air heat pump?
An air to air heat pump takes heat from the outside air using electricity and delivers it indoors through fan units that circulate warm air. It uses no radiators or underfloor pipework and often does not provide hot water. Most models can also cool, so it looks and works much like an air conditioning system.
Key points
- It moves heat from outdoor air to indoor fan units. There is no wet heating system, and many models do not make hot water.
- GOV.UK lists a £2,500 Boiler Upgrade Scheme grant for an air-to-air heat pump, compared with £7,500 for an air source heat pump that heats water.
- To count under MCS, a system must be optimised to heat the whole property, and cooling-only systems are excluded.
- MCS's consumer page says no installers are yet certified to install air-to-air heat pumps, so check the position before you rely on the grant.
- Refrigerant runs between indoor and outdoor units, so the installation needs F-gas qualified engineers.
How an air to air heat pump works
An air to air heat pump transfers heat from the outside air into your home using electricity. Instead of passing the heat to water for radiators or underfloor pipes, it delivers it through fans that circulate warm air.[1]MCS, Air-to-Air Heat Pumps An outdoor unit, usually on a wall or the ground, is linked by pipework to indoor units that are often wall-mounted, much like air conditioning.[1]MCS, Air-to-Air Heat Pumps
Most products can also cool on hot days. MCS says systems that are certified under its scheme must be optimised to heat the whole property, must not be optimised for cooling, and that cooling-only systems are excluded.[1]MCS, Air-to-Air Heat Pumps Our page on air conditioning versus a heat pump covers the overlap. A split system air conditioner is built the same way, and an inverter air conditioner varies its output to match demand.
Many air to air heat pumps do not provide hot water. If you want hot water from the same system, you may need an extra system for it.[1]MCS, Air-to-Air Heat Pumps
Air to air compared with air to water
| Air to air | Air to water | |
|---|---|---|
| How heat is delivered | Fans in indoor units | Radiators, underfloor heating and a hot water cylinder |
| Hot water | Usually not provided | Can heat hot water |
| Pipework carries | Refrigerant between indoor and outdoor units | Water between the unit and the heating system |
| Boiler Upgrade Scheme grant | £2,500 | £7,500 |
| Typical use | Homes without wet heating, such as flats or all-electric homes | Homes with radiators or underfloor heating |
The grant figures come from GOV.UK.[3]GOV.UK, Apply for the Boiler Upgrade Scheme: What you can get The Heating and Hotwater Industry Council says air-to-air systems typically do not produce hot water and cannot be installed in kitchens or bathrooms without ducting, and that they offer an alternative to electric storage heaters and direct electric heating in all-electric, off-gas homes.[4]Heating and Hotwater Industry Council, Air-to-air heat pumps added to Boiler Upgrade Scheme See also our page on the air to water heat pump.
Where MCS certification stands
GOV.UK lists £2,500 towards an air-to-air heat pump under the Boiler Upgrade Scheme, alongside the £7,500 for an air source heat pump.[3]GOV.UK, Apply for the Boiler Upgrade Scheme: What you can get But MCS certification is a separate step. MCS says air-to-air heat pumps are being incorporated into the scheme, and that at the time of its page no installers were yet certified to install them.[1]MCS, Air-to-Air Heat Pumps
The latest MCS update, published on 8 September 2026, says a number of MCS certified air-to-air products are now in the Product Directory. It says the installer certification bodies are working towards UKAS accreditation, after which installers can apply for certification. The technical supervisor on an air-to-air installation must hold competence in refrigeration, air conditioning and heat pumps at Level 3 or above.[2]MCS, Implementation of air-to-air heat pumps into MCS enters next phase Check the current position with an MCS certified installer or the MCS website before you rely on the grant.
The Heating and Hotwater Industry Council adds that installations must be carried out by F-gas qualified engineers, because the refrigerant is carried in pipework between the indoor and outdoor units.[4]Heating and Hotwater Industry Council, Air-to-air heat pumps added to Boiler Upgrade Scheme Do not let anyone without the right qualification work on the refrigerant circuit.
Example
Leena lives in a flat in Bradford with electric storage heaters and no radiators. A wet system would need pipework she does not have. She asks BASI about an air to air system. The engineer explains that it would heat rooms with wall units but would not heat her water, so she keeps her cylinder. Before she commits, BASI checks whether the £2,500 grant can currently be claimed through an MCS certified installer.
What people get wrong
People often think “heat pump” always means radiators and hot water. An air to air heat pump heats air. MCS notes that many models do not provide hot water, and that to be MCS certified a system must be designed mainly for heating rather than cooling.
The second mistake is to assume the grant is available just because GOV.UK lists it. MCS says installers were not yet certified at the time of its page, and the grant needs MCS certification.[1]MCS, Air-to-Air Heat Pumps Always confirm the current position before signing.
The bottom line
An air to air heat pump takes heat from outdoor air and delivers it through indoor fan units, like a reversible air conditioner optimised for heating. GOV.UK lists a £2,500 grant towards one, but MCS certification for installers was still being put in place at its latest update. It suits homes with no wet heating system, and it needs F-gas qualified engineers. See our air conditioning page for the equipment side.
Common questions
Is an air to air heat pump the same as air conditioning?
They use the same technology. MCS says air-to-air heat pumps work like air conditioning, with an outdoor unit linked by pipework to indoor units. To be MCS certified a system must be optimised for heating, while cooling-only systems are excluded.
Can I get a grant for an air to air heat pump?
GOV.UK lists £2,500 towards an air-to-air heat pump under the Boiler Upgrade Scheme, if you are replacing a fossil fuel heating system. MCS says installers are not yet certified for them, so ask whether the grant can currently be claimed.
Does an air to air heat pump heat my water?
Usually not. MCS says many air-to-air heat pumps do not provide hot water, so you may need another system for it. An air to water heat pump heats radiators and a hot water cylinder.
Who can install an air to air heat pump?
The industry body HHIC says the refrigerant is carried in pipework between indoor and outdoor units, so installations must be done by F-gas qualified engineers. Under MCS the technical supervisor must hold refrigeration, air conditioning and heat pump competence at Level 3 or above.
Sources
We cite the original source for every figure: government, regulators, standards bodies and manufacturers' own documents. Each one shows the date we last checked it.
- MCS. Air-to-Air Heat Pumps. Checked 11 November 2026. ↩
- MCS. Implementation of air-to-air heat pumps into MCS enters next phase. Checked 11 November 2026. ↩
- GOV.UK. Apply for the Boiler Upgrade Scheme: What you can get. Checked 11 November 2026. ↩
- Heating and Hotwater Industry Council. Air-to-air heat pumps added to Boiler Upgrade Scheme. Checked 11 November 2026. ↩