Kit desk · chart page
Air to air vs air to water heat pump
Air to air vs air to water heat pump grants differ threefold: £2,500 for air-to-air and £7,500 for air-to-water under the Boiler Upgrade Scheme in England and Wales.
By the Cooler Indoors desk · figures checked · 4 charts · sources · methods
Choosing between an air-to-air and an air-to-water heat pump comes down to what you want heated. An air-to-air unit warms, and usually cools, the air in rooms through wall or ceiling units; an air-to-water unit heats water for radiators, underfloor pipes and a hot water cylinder. Grants, costs and installer rules differ as well.
What does each type of heat pump actually heat?
An air-to-air heat pump heats room air and nothing else. The glossary in the government's Boiler Upgrade Scheme statistics describes it as taking heat from outside air and using it to warm air for space heating, so it makes no hot water. An air-to-water system feeds a wet central heating circuit and a cylinder, which is why it can take over every job a gas boiler does.
Most air-to-air units can also run in reverse to cool rooms in summer. That dual role is the main draw for UK households weighing air conditioning: one outdoor unit, warmth in winter, cooler bedrooms in a heatwave.
How do Boiler Upgrade Scheme grants compare for air to air and air to water?
GOV.UK lists £7,500 towards an air-to-water heat pump and £2,500 towards an air-to-air one, in England and Wales. The air-to-air grant became law on 28 April 2026 and is for homes only; the regulations exclude non-residential buildings. Homes heated by oil or LPG can claim £1,500 more for air-to-water until 31 March 2027, but that top-up does not extend to air-to-air.
Source: GOV.UK, Apply for the Boiler Upgrade Scheme: what you can get · checked 29 October 2026
How we read this Grant amounts in England and Wales as listed on 29 October 2026. The off-gas top-up ends on 31 March 2027, and the air-to-air grant still needs an MCS installer.
Show the numbers
| Label | £ | Note |
|---|---|---|
| Air-to-water, off-gas home | £9,000 | |
| Air-to-water | £7,500 | |
| Ground source | £7,500 | |
| Biomass boiler | £5,000 | |
| Air-to-air | £2,500 |
There is a catch. BUS pays out only through an MCS certified installer, and in an update dated 8 September 2026 MCS confirmed that no installer can yet hold that certification for air-to-air. So the £2,500 is in law but may not be claimable yet; check with Ofgem before you sign anything. MCS adds a design rule too: an air-to-air system on its books has to cover 100% of the property's heating requirement, which a unit sized for one bedroom would not.
Source: DESNZ, Boiler Upgrade Scheme statistics, September 2026 · checked 29 October 2026
How we read this Cumulative voucher applications from Table 1.1. Air-to-water has been eligible for years, air-to-air only since April 2026, so part of the gap is timing.
Show the numbers
| Label | applications | Note |
|---|---|---|
| Air-to-water | 157,573 | |
| Air-to-air | 157 | No vouchers issued |
Can you get a heat pump grant in Scotland or Northern Ireland?
Yes for air-to-water in Scotland, no for air-to-air anywhere outside England and Wales. Home Energy Scotland pays up to £7,500, with the same sum again available as a loan at no interest, but only for heat pumps that supply all heating and hot water; it names air-to-air units as ineligible. Northern Ireland has no heat pump grant open, though installed heat pumps there now carry 0% VAT.
On video: What is an Air to Air heat pump?
“What is an Air to Air heat pump?”, a video from the DaikinUK channel on YouTube. Daikin UK explains that air-to-air units heat and cool rooms but do not make hot water or work with radiators, and says that is what an air-to-water system does. It is their video, not ours, and it loads from YouTube only when you press play.
Source: Home Energy Scotland, grants and loans · checked 29 October 2026
How we read this Grant per home, not loans. Zero means no scheme open to air-to-air on 29 October 2026; the English and Welsh figure is from GOV.UK and depends on MCS certification.
Show the numbers
| Label | £ | Note |
|---|---|---|
| England | £2,500 | |
| Wales | £2,500 | |
| Scotland | £0 | |
| Northern Ireland | £0 |
How much does an air to water heat pump cost to install, and what about air to air?
For air-to-water, BUS records put the median installed cost at £12,826 for July to September 2026. Since 2022 the quarterly median has moved only between £12,082 and £13,600. For air-to-air, the BUS tables hold no cost data yet and we found no other primary figure, so we give none. The quarter-by-quarter detail sits on our installation cost tracker.
Source: DESNZ, Boiler Upgrade Scheme statistics, Table Q1.1A · checked 29 October 2026
How we read this Nominal costs, grant included, England and Wales. These are air-to-water systems with a cylinder and pipework; they say nothing about what an air-to-air install costs.
Show the numbers
| Label | Median | Lower quartile | Upper quartile | Note |
|---|---|---|---|---|
| 2022 Q2 | £13,182 | £10,913 | £15,205 | |
| 2022 Q3 | £12,860 | £10,976 | £15,000 | |
| 2022 Q4 | £12,969 | £10,794 | £15,132 | |
| 2023 Q1 | £13,256 | £10,880 | £15,800 | |
| 2023 Q2 | £13,400 | £11,056 | £15,940 | |
| 2023 Q3 | £13,495 | £11,190 | £15,995 | |
| 2023 Q4 | £13,600 | £11,200 | £16,170 | |
| 2024 Q1 | £13,000 | £10,731 | £15,778 | |
| 2024 Q2 | £12,800 | £10,385 | £15,500 | |
| 2024 Q3 | £12,599 | £10,313 | £15,300 | |
| 2024 Q4 | £12,500 | £10,177 | £15,199 | |
| 2025 Q1 | £12,082 | £9,835 | £15,000 | |
| 2025 Q2 | £12,500 | £10,029 | £15,246 | |
| 2025 Q3 | £13,000 | £10,863 | £15,580 | |
| 2025 Q4 | £13,437 | £11,459 | £16,030 | |
| 2026 Q1 | £13,103 | £11,348 | £15,789 | |
| 2026 Q2 | £12,900 | £11,125 | £15,636 | |
| 2026 Q3 | £12,826 | £10,717 | £15,461 | Latest |
Which heat pump works with radiators and a hot water cylinder?
Only air-to-water. It heats the water that runs through radiators or underfloor loops, and it heats a stored-water cylinder for taps and showers. An air-to-air system leaves your hot water to something else, which matters for grants: BUS expects fossil-fuel heating to be replaced and pays nothing for a hybrid system, so if a boiler is staying, ask Ofgem whether you still qualify.
Both types count as installed air source heat pumps for VAT, which HMRC zero-rates until 31 March 2027.
What safety rules apply when a gas boiler is involved?
Any work on the boiler itself is Gas Safe work: HSE requires Gas Safe registration for anyone paid to touch a gas appliance in a home. The heat pump side has its own trades. A split air-to-air system needs an F-gas certified engineer and company for the refrigerant pipework, and a new circuit needs a registered electrician.
Smell gas, or hear a carbon monoxide alarm? Get every person out of the house first. While inside, leave light switches, phones and all other electrical items alone. Once outdoors, ring the National Gas Emergency Service, 0800 111 999, or dial 999 if anyone is unwell.
| Point | Air-to-air | Air-to-water | Source |
|---|---|---|---|
| What it heats | Room air; most models also cool | Water for radiators or underfloor, plus a cylinder | DESNZ BUS statistics |
| BUS grant, England and Wales | £2,500, homes only | £7,500, or £9,000 off-gas to 31 March 2027 | GOV.UK |
| Law and start date | SI 2026/390, from 28 April 2026 | In the scheme since it opened | SI 2026/390 |
| Installer certification | MCS route not open yet (8 September 2026) | MCS certified installer | MCS, Ofgem |
| Scotland | Not eligible | Up to £7,500 grant plus £7,500 optional loan | Home Energy Scotland |
| Gas work and CO | Gas Safe engineer for any boiler work | Gas Safe engineer for any boiler work | HSE gas FAQs, HSE CO advice |
Questions this data raises
Can an air-to-air heat pump replace my gas boiler completely?
It can heat the rooms but not your water, so another water heater would be needed. Under MCS rules an air-to-air system must also cover the whole home's heating need.
Can a shop or office get BUS money for an air-to-air unit?
No. The 2026 amendment regulations say an air-to-air heat pump is not eligible plant for a non-residential building.
Why does the cost chart leave out air-to-air installs?
The BUS cost tables show no data for air-to-air yet, and no air-to-air vouchers had been issued by the end of September 2026. We will not fill the gap with unsourced prices.
If I fit air-to-air, what happens to my hot water?
Nothing changes: an air-to-air system heats and cools room air only. Hot water still needs its own source, such as the existing boiler, an immersion heater or a separate heat pump cylinder.
Do I need planning permission for the outdoor unit?
In England a unit that heats can fall under permitted development, within limits on size, number and noise; a cooling-only unit cannot. Check with your council's planning team before buying.
Sources for this page
- GOV.UK, Apply for the Boiler Upgrade Scheme: what you can get gov.uk
- DESNZ, Boiler Upgrade Scheme statistics, September 2026 gov.uk
- Home Energy Scotland, grants and loans homeenergyscotland.org
- SI 2026/390 legislation.gov.uk
- MCS mcscertified.com
- Ofgem ofgem.gov.uk
- HSE gas FAQs hse.gov.uk
- HSE CO advice hse.gov.uk
All checked 29 October 2026. How we choose and read sources: Methods & sources.