Air-to-air heat pumps

What an air-to-air heat pump is

An air-to-air heat pump takes heat from the outside air and delivers it into your rooms as warm air, through indoor units on the wall, floor or ceiling. In summer it runs in reverse and cools. If that sounds like air conditioning, it is: the Energy Saving Trust notes that air-to-air heat pumps are sometimes referred to as air conditioning (Energy Saving Trust: air-to-air heat pumps). The difference is in how the system is designed and used. A heat pump designed as your main heating has to be sized for the coldest weather and every room that needs heat, not just the rooms you want to cool in a heatwave.

An air-to-air system doesn’t heat water, so you need a separate way to make hot water, such as an electric cylinder. If you want the heat pump to run radiators or underfloor heating and the hot water, an air-to-water heat pump is the right type.

When it makes sense

• Homes heated by storage heaters, panel heaters or other electric heating, where there are no radiators to connect a heat pump to.
• Homes on oil or LPG where you want to replace the boiler and would also like cooling in summer.
• Flats and smaller homes where a hot water cylinder and new radiators would be hard to fit.
• Extensions, garden rooms and loft rooms that need their own heating and cooling, even where the grant doesn’t apply.

It is less suited to a home where everyone wants silent, hidden heating with no indoor units, or where you would rather keep the radiators. We talk through the alternatives on the survey.

The £2,500 Boiler Upgrade Scheme grant

In England and Wales, the Boiler Upgrade Scheme gives £2,500 towards an air-to-air heat pump, but only when strict conditions are met (GOV.UK: what you can get). In summary:

• It must replace the home’s existing fossil-fuel heating, such as a gas, oil or LPG boiler.
• It must meet the home’s full heating demand, not just one or two rooms.
• It must be installed by an MCS certified installer.
• It is for homes only, and not alongside a boiler as an add-on. Hybrid systems are excluded.
• There is one grant per property, and you can’t get a grant to replace an existing low-carbon system.

The installer applies for the grant. Air conditioning added to a home that keeps its boiler doesn’t qualify. Our article on the air-to-air heat pump grant goes into the detail. This is general information; the scheme rules decide eligibility.

Designing for the whole home

To heat a home on its own, the system has to be designed properly. We survey every room, measure it, look at the windows, walls, insulation and draughts and calculate how much heat each room loses on a cold day. That sets the size of each indoor unit and the outdoor unit. Most whole-home air-to-air systems are multi-split systems, with one outdoor unit serving several rooms, or more than one outdoor unit in a larger home.

We also look at where indoor units can go so warm air reaches the room evenly, where the outdoor unit can sit without bothering you or the neighbours, how pipework and condensate drains will run and whether the electrical supply needs upgrading. As NICEIC approved contractors, we can install the circuits as part of the job.

Planning permission and noise

Since 2025, air-to-air heat pumps on houses in England can be permitted development, on the same kind of conditions as other air source heat pumps. Those include an outdoor unit of no more than 1.5 cubic metres, compliance with MCS 020(a), which includes a noise check, and rules on where the unit can go, such as not on a pitched roof. Listed buildings, conservation areas, flats and areas with an Article 4 direction have extra limits (Planning Portal). A system that is used only for cooling isn’t covered by these rights, so check with your council. We check the position and noise on the survey. This is general information, not planning advice.

VAT and cost

HMRC zero-rates the installation of energy-saving materials in homes from 1 May 2023 to 31 March 2027, then 5%. Air source heat pumps qualify if they are permanently fixed, and HMRC says most air conditioning units are air source heat pumps, although whether a product qualifies depends on the facts (HMRC Notice 708/6). We confirm the VAT on your quote. This is general information, not tax advice.

Whole-home air-to-air systems are priced after the survey because the number of rooms and the heat loss vary so much. As a guide, our multi-split installations are typically £2,800–£4,500 + VAT for two rooms and £4,500–£8,500 + VAT for three to five rooms, including supply, installation, commissioning and F-Gas documentation. The grant, where you are eligible, comes off the price.

Warranty and aftercare

Your heat pump comes with the manufacturer’s warranty, on the manufacturer’s terms. These vary by brand, and for example Daikin’s standard warranty on split air conditioning is 2 years (Daikin UK warranty). We explain the terms for the model we quote. An annual service keeps the filters, coils and drains clean so the system heats efficiently through the winter.