By Bournemouth Air Conditioning. Published .
In England, a home air conditioning unit that heats as well as cools can often be installed without planning permission, because it counts as an air source heat pump under permitted development rules. A cooling-only unit is not covered, and listed buildings and some homes in conservation areas need permission either way.
The rules were updated in May 2025. Here is how they work, and what to check before you book an install.
Why heating and cooling matters
Most modern wall-mounted air conditioning units are reversible. They work as a heat pump, moving heat out of the room in summer and into it in winter. Planning rules in England treat the outdoor unit of a heat pump as permitted development, under what is known as Class G.
Since 29 May 2025, one of the conditions is that the heat pump is not used solely for cooling. Council guidance, for example from Bracknell Forest Council, puts it simply: the unit can be heating only or combined heating and cooling, but not cooling only. A cooling-only system does not get the permitted development allowance, so it may need a planning application.
If you are not sure whether a unit is reversible, check the model's specification. A heat pump will list a heating capacity as well as a cooling capacity.
The main permitted development conditions
Under the rules that came into force on 29 May 2025, the outdoor unit generally counts as permitted development on a house if:
- It is not used solely for cooling.
- There is no more than one heat pump on a semi-detached or terraced house, or no more than two on a detached house.
- The outdoor unit is no bigger than 1.5 cubic metres. On a block of flats the limit is one unit of no more than 0.6 cubic metres.
- The installation meets the MCS 020(a) noise standard, which is the calculation installers use to check sound levels at the nearest neighbour.
- The building is not listed and is not a scheduled monument.
The outdoor unit should also be sited to keep its effect on the look of the building and the neighbourhood as small as practical. That is good practice anyway.
Conservation areas and listed buildings
If your home is listed, you will need listed building consent for an outdoor unit, and often for the pipe run through the wall too.
In a conservation area, council guidance says the unit cannot go on a wall or roof that faces a road, or closer to the road than the nearest part of the house. A side or rear wall is usually the answer.
Dorset has a lot of period housing and conservation areas, particularly in towns such as Wimborne. Siting an outdoor unit there needs care and sometimes consent. We survey for it rather than discovering it on installation day.
Flats and leasehold homes
Flats have their own, tighter limits, and the decision usually is not yours alone. If you are a leaseholder, your lease will almost certainly need the freeholder's permission for anything fixed to the outside walls. Check your lease and ask the managing agent before you book a survey.
Other rules that apply to every install
- F-Gas. Anyone installing, servicing or repairing a system containing fluorinated refrigerant must hold F-Gas certification. Ask for the engineer's certification number.
- Electrics. Adding a new circuit for an air conditioning unit is usually notifiable electrical work under the Building Regulations, so it must be done or signed off by someone qualified to certify it.
- Noise. Even where permission is not needed, a noisy outdoor unit next to a neighbour's bedroom window causes problems. Siting is worth getting right first time.
Who to ask in the Bournemouth area
If you are not sure, ask your council before work starts. Many councils offer pre-application advice, sometimes for a fee. A lawful development certificate gives you written confirmation that no planning application is needed, which can help when you sell.
- Bournemouth, Christchurch and Poole: BCP Council.
- Wimborne, Ferndown and the rest of East Dorset: Dorset Council.
- Ringwood: New Forest District Council, or the New Forest National Park Authority if you are inside the National Park.
Book a survey or service
We check siting and any planning issues at the free survey, before anything is ordered. See our air conditioning installation and home air conditioning pages, or the local pages for Bournemouth and Wimborne. Call 07910 686513 to book a survey.
Related services: Air conditioning installation, Home air conditioning.