Air to air heat pumps for rental properties

How an air to air heat pump works

An air to air heat pump moves heat from outside air into the rooms of a home, and delivers it as warm air. An outdoor unit does the heat extraction. Refrigerant pipes carry that heat indoors to one or more indoor units on walls, floors or ceilings, which blow warm air into the room. Most people know the same hardware as a split system air conditioner that also heats.

Because it moves heat rather than making it, it delivers more heat than the electricity it uses. That ratio is the seasonal coefficient of performance (SCOP), and a higher SCOP means a lower running cost. Ask any firm quoting for the SCOP of the specific model.

There is no wet system. No radiators, no pipework through the floors, no cylinder. That is the main reason landlords look at the technology, and also the source of its main limit.

What it does not do: hot water

An air to air heat pump makes no hot water. Each indoor unit heats air only, so the property needs a separate way to heat water for baths, showers and taps. In most rentals that means whatever is there already: an immersion cylinder, an electric shower, a combi boiler kept for water, or a point of use heater.

This matters for three reasons:

• If the existing hot water comes from a gas boiler, fitting an air to air system does not remove the gas appliance. You keep a boiler and its annual safety check. See the landlord gas safety certificate guide.
• Any saving applies to space heating only. The energy used for hot water stays as it is today.
• Funding rules can bite: the grant is for a heat pump that replaces existing heating, so a property where the boiler stays for hot water needs checking before anyone orders equipment.

Where it fits in a rental

An air to air system fits best in a small, well insulated, electrically heated home. The typical cases:

• Flats with storage heaters or panel heaters. There is no pipework to reuse and often no space for a cylinder. One outdoor unit and one or two indoor units can replace the lot. See also heat pumps for flats.
• Studios and one bedroom lets where a single indoor unit can serve a large share of the floor area.
• Homes with no gas connection where the alternative is a full wet system with an outdoor unit, cylinder and new radiators.

It fits poorly in a large house with many closed rooms, because each room that needs its own heat needs its own indoor unit. Bedrooms with the doors shut will not be warmed by an indoor unit in the hallway.

The £2,500 Boiler Upgrade Scheme grant

The Boiler Upgrade Scheme pays £2,500 towards an air to air heat pump. Landlords can apply, because the rules cover a property you own and rent out to tenants. The grant has limits that matter for rentals:

Condition	What it means
Replaces existing heating	The new system must replace a fossil fuel or electric heating system such as oil, gas, electric or LPG
Homes only	Residential properties; most new builds and social housing are excluded
Not already funded	A property that has had government funding for a heat pump or biomass boiler is excluded
One grant per property	No second grant for the same address
Installer applies	An MCS certified installer applies for you; you do not claim it yourself

The grant cannot go to replace an existing low carbon heating system. Ask any firm quoting to show how the £2,500 appears on the quote, and read it line by line. Source: GOV.UK, check if you are eligible and what you can get. For the wider scheme see the Boiler Upgrade Scheme for landlords.

Costs vary with the number of indoor units, so get written quotes that state how many rooms each one serves.

Noise and planning

Noise from the outdoor unit is the most common complaint a landlord hears, from neighbours as well as tenants. Under the permitted development rules for air source heat pumps in England (Class G), a unit can be installed without a planning application only if it meets set conditions. For a heat pump the planning route points to a noise limit of 37.0 dB(A) under MCS 020 (a). The main siting rules are:

• One unit on a house that is not detached or on a block of flats, and up to two on a detached house.
• The compressor unit up to 1.5 cubic metres on a house, and 0.6 cubic metres on a block of flats.
• No unit on a pitched roof.
• Tighter limits apply in conservation areas and for listed buildings, and an Article 4 direction can remove permitted development rights altogether.

The wording of these rules was amended in May 2025, and the legislation does not say in terms whether a split air to air system counts as an air source heat pump for Class G. Ask the installer to confirm in writing how the council will treat the proposal. On a flat, you also need the freeholder or management company to agree to an outdoor unit on a wall or balcony, which is a lease question, not a planning one. Source: legislation.gov.uk, Class G.

Tenants, filters and maintenance

Tenants use air to air systems directly, because the remote control is in the room. That is an advantage over a wet system, which is mostly set and forgotten, and it is also where the risk sits.

The practical points:

• Filters. Indoor units have air filters that collect dust and need regular cleaning at the interval the manufacturer sets. Put the manufacturer’s cleaning instructions in the tenancy information pack, and agree who does it.
• Servicing. Ask the installer what annual check the manufacturer requires to keep the warranty, and who pays. Building it into your own property inspections is cheaper than a failed unit.
• Controls. Running a unit on a high setting with a window open wastes the tenant’s money. A short written guide to set points helps.
• Condensate. The units drain water, so check the drain route at fitting.
• Who pays the bills. Where the tenant pays the electricity, running cost information belongs in the letting conversation. See heat pump running costs for tenants.

Section 21 ended in England on 1 May 2026 and assured shorthold tenancies became periodic assured tenancies, so write down who looks after the equipment at the start of the tenancy rather than relying on a later conversation.

Cooling as a bonus

Many air to air units can run in reverse and cool a room in summer. For a landlord this is a lettability point, not a compliance point: top floor flats and south facing rooms get hot, and a unit that cools is something a tenant can see. Treat it as a bonus rather than the reason to buy.

Cooling raises electricity use, and where the tenant pays the bills they pay for it. Say so in the tenancy information. Check that the model you are quoted for has a cooling mode.

Does it help the EPC?

It may, but this page cannot give a firm answer, so check before you rely on it. The government has said, in its consultation on the Home Energy Model for EPCs, that electric heat pumps would always score a C and above on a planned heating system metric. That text does not single out air to air units, and the metric is not yet law. Source: DESNZ, Home Energy Model for EPCs.

This guide could not verify on a primary source is how a current EPC assessor records an air to air system, and whether it scores like a wet heat pump. The practical steps:

• Look at your current EPC on the GOV.UK register and note the main heating line and its recommendations.
• Ask a domestic energy assessor how they would record the new system, before you commit, and get the answer in writing.
• Do not assume a band. The result depends on the property and on how the assessor records the system.

Today’s legal minimum for most rentals is EPC E. The planned standard is EPC C by 1 October 2030, but the regulations have not been laid. See do heat pumps improve an EPC rating and the EPC C 2030 and your heating choice.

Air to air or a wet system?

An air to air system wins on installation effort and upfront cost in a small home. A wet system wins on hot water and on covering a whole house. The decision comes down to a few points:

Question	Points to air to air	Points to a wet system
Property size	Flat, studio, one or two bedrooms	Larger house with many rooms
Current heating	Electric heaters, no pipework	Working radiators and a boiler
Hot water	Already handled separately	Needs replacing
Grant	£2,500	£7,500 (air to water, mains gas homes)
Works inside	Wall brackets, small pipe runs	New cylinder, possibly new radiators

On running costs the picture depends on what you replace. The Ofgem price cap from 1 October to 31 December 2026 sets electricity at 26.32p per kWh and gas at 7.97p per kWh. Source: Ofgem.

Worked example (modelled, not a real project). Inputs: electricity 26.32p/kWh, gas 7.97p/kWh, a gas boiler at 90% efficiency (assumption), a heat pump SCOP of 3.0 (assumption, the low case in this site’s illustrative model). Each kWh of heat from gas costs about 8.9p (7.97 divided by 0.9). Each kWh from the heat pump costs about 8.8p (26.32 divided by 3.0). Each kWh from a direct electric heater costs 26.32p. So a heat pump at SCOP 3.0 roughly matches gas per unit of heat and costs about a third of direct electric heating. The saving case is the electrically heated rental, not the gas one.

When this is not the right answer

Skip an air to air system, or look at other options first, in these cases:

• The home is poorly insulated. Loft insulation, draught proofing or wall insulation can cut the heat needed, which lets you fit a smaller unit or avoid one. See before you install a heat pump in a rental.
• The property needs hot water and heating together and has a working gas boiler. Replacing the boiler’s heating role while keeping it for water gives less than it seems.
• The grant is the reason. If the system would not replace existing heating, the £2,500 may not apply.
• The tenant will not use it properly, or you cannot get consent for the outdoor unit in a flat.
• The property is a large house with many separate rooms, where a wet system is usually simpler.

Other funding routes have different rules and are covered in the grants and funding guide.

Next step

Work out whether the numbers hold for your property with the heat pump landlord calculator, or send an enquiry through the quote page and relevant independent firms will contact you. There is no charge to you and no obligation.