Planning permission

Do you need planning permission for air conditioning?

It depends on one thing more than any other: whether the outdoor unit can also heat. A lot of what you will read online glosses over that, so here is the honest version for England.

The short answer

Used only for cooling? Permission is needed.

Class G carries a condition that the unit is not used solely for cooling. So a cooling-only unit needs planning permission — and so does a reversible unit that is only ever used to cool, because the condition is about how it is used, not only what it can do.

Heats as well as cools? Often permitted development.

Air source heat pumps used for heating were already covered. What changed on 29 May 2025 is that units which also cool were brought in, so a reversible air-to-air heat pump on a house can now fall under Class G provided it stays inside the limits below.

Your council still has the final say.

Permitted development is not a guarantee. If anything is borderline, a Lawful Development Certificate from your local planning authority puts it beyond doubt.

The Class G limits, in plain English

  • The outdoor unit must be no more than 1.5 cubic metres on a house — and no more than 0.6 cubic metres on a block of flats.
  • Up to two units on a detached house; one on a semi-detached or terraced house; one on a block of flats.
  • The installation must meet the MCS 020 a) noise standard, which limits the sound level at your neighbour's nearest window or door. Since 29 May 2026 the older “or equivalent standard” allowance has gone, so MCS 020 a) is the only one that counts.
  • It cannot go on a pitched roof, and on a flat roof it must sit at least a metre from the edge.
  • It cannot go on a wall fronting a highway above ground-floor storey level — that restriction applies to ordinary houses, not only to protected areas.
  • The old rule requiring the unit to sit a metre from your boundary no longer applies, so it can now be positioned nearer a fence — subject to meeting the noise standard above.
  • The unit must be removed when it is no longer needed.

When the answer changes

Listed buildings

Class G does not apply at all to a listed building, or anywhere within its curtilage — including a unit standing in the garden. That means you need planning permission as well as listed building consent. Consent is not optional: unauthorised work to a listed building is a criminal offence, so check this one first.

Conservation areas and other protected land

There are two tests, and both must be met. The unit must not go on a wall or roof fronting a highway, and it must not be nearer to any highway bounding the property than the nearest part of the house itself — so a front-garden position is usually out.

Flats and leasehold

As well as the tighter 0.6 cubic metre limit on a block of flats, you will usually need your freeholder's or management company's consent under the terms of your lease. That is a separate matter from planning.

Renting

Permission from your landlord is needed regardless of what the planning rules say.

Commercial premises

Different rules apply to commercial buildings, and larger installations more often need a planning application.

How to check your own property

  1. Check the unit heats — and that you will use it for heatingPermitted development depends on the unit not being used solely for cooling. Ask for the model, confirm it provides a heating function, and be aware the condition follows how you actually use it.
  2. Check what your property isHouse or block of flats, detached or terraced, listed or not, inside a conservation area or not. Your council's website will confirm listing and conservation status.
  3. Check where the unit would goSize, position, distance from the roof edge, whether it would sit on a highway-facing wall above ground-floor level, and how it sits relative to any highway bounding the property.
  4. Ask your council if it is closeA Lawful Development Certificate is the formal way to confirm that permission is not needed. It costs less than a full application and removes the doubt.

Common questions

Does an air conditioning unit really always need planning permission if it only cools?

In England, yes — where it is used solely for cooling. The Class G condition is that the unit is not used solely for cooling, so a cooling-only installation needs a planning application. In practice an outdoor condenser materially changes the external appearance of the building, so a modest size does not remove the need. If you are fitting a reversible unit and will genuinely use it for heating too, permitted development may be open to you — which is why it is worth checking your own case rather than relying on a blanket statement either way.

What happens if it is installed without permission?

The local planning authority can ask for a retrospective application and, if it is refused, require the unit to be removed. On a listed building the position is far more serious, as unauthorised work is a criminal offence.

Does my neighbour have to agree?

Your neighbour's agreement is not a planning requirement, but noise is. The MCS 020 standard sets a limit measured at their nearest window or door, and a persistent noise problem can be pursued separately as a statutory nuisance, so position and mounting are worth getting right.

Is this the same across the UK?

No. The rules described here are for England. Scotland, Wales and Northern Ireland have their own permitted development regimes, so check with the relevant authority.

Can you tell me whether I need permission?

We can tell you what normally applies to a property like yours and flag anything that looks like it needs confirming, and we will say so plainly rather than assume. Only your local planning authority can give a binding answer.

About this guide

This is general information about the rules in England, not legal or planning advice, and the rules change. The Planning Portal is the government's own guidance, and your local planning authority is the only body that can confirm your case. Planning Portal