The short answer for homes in England
A domestic air-to-air heat-pump installation may be permitted development when every relevant limit and condition is met. The rules changed on 29 May 2025 so qualifying equipment that provides cooling as well as heating can use the air-source heat-pump permitted development right.
That does not make every outdoor air-conditioning unit automatically permitted. The current Planning Portal guidance says the installation must not be solely for cooling, must meet the applicable MCS planning standard, must stay within size and siting limits, and must minimise its effect on appearance and local amenity.
The checks that can change the answer
Start with the exact property and proposed outdoor position. Flats, listed buildings, conservation areas, World Heritage Sites and elevations facing a highway have additional constraints. Permitted development rights may also have been removed by a planning condition or Article 4 direction.
For houses, the Planning Portal currently states a maximum outdoor compressor volume of 1.5 cubic metres; for a block of flats it states 0.6 cubic metres. Detached houses can have different numerical limits from attached homes or blocks of flats. Because these conditions are cumulative, meeting one does not prove the whole proposal qualifies.
Noise and neighbour amenity
The relevant test is not simply whether a product brochure describes a unit as quiet. Position, reflective walls, barriers, height and the nearest neighbouring habitable-room opening all affect the assessment.
A survey should therefore show a real outdoor position and obtain the model-specific sound data. Moving a unit around a corner or changing the system arrangement can alter both planning risk and the experience of the neighbour without changing the indoor brief.
Flats, leases and managed buildings
Planning permission and private consent are separate. A proposal may satisfy planning rules and still need written freeholder, landlord or management-company approval because the unit, wall penetration, route or drain affects common or external parts.
Before asking for consent, prepare a concise pack: unit model and dimensions, proposed location, pipe route, condensate plan, electrical route, sound information and an annotated photograph. A vague request is more likely to be delayed or rejected.
Listed buildings and sensitive streets
Listed building consent may be needed for alterations affecting character, even where ordinary planning permission would not be. Bath and parts of Bristol contain many sensitive façades, so a prominent condenser or long run of containment can be a decisive issue.
Early design is the useful response: compare rear or secondary elevations, ground-level positions, screened locations and routes that avoid important fabric. The aim is not to hide a bad proposal in paperwork; it is to improve the physical proposal before permission is sought.
A safe order of work
First define the indoor requirement. Second, survey one or more viable outdoor positions and routes. Third, check planning status and private consents against that actual proposal. Only then should equipment be ordered and an installation date fixed.
RyRow can supply the practical system information used in those checks. The property owner remains responsible for obtaining any formal planning, listed-building, landlord, freeholder or management approval unless a separate written service says otherwise.
Primary sources