Planning permission for air conditioning

For most houses in England, no. The rules changed on 29 May 2025 and they got considerably more generous, including for systems that cool as well as heat.

That last part matters. Before the change, permitted development covered air source heat pumps used for heating. Systems that also cooled sat in a grey area that made some councils awkward. They are now explicitly in scope.

What permitted development allows

For a house in England, an outdoor unit is permitted development if it meets all of these:

The unit is no more than 1.5 cubic metres, including its housing
Two units on a detached house, one on anything else
It meets the MCS 020 noise standard, which is 42 dB(A) measured at the nearest neighbouring habitable room window
It is not used solely for cooling, so a heat and cool system qualifies where a cooling only one does not
It is not on a pitched roof. On a flat roof it must sit at least a metre from the edge
It is not on a wall above ground floor level where that wall faces a highway

The old requirement to keep the unit a metre from the boundary has gone entirely. That single change made a great many small terraced yards viable that previously were not.

Where it does not apply

Listed buildings have no permitted development rights at all. Anything fixed to the structure needs listed building consent, and that is a real application with a real timescale rather than a formality.

Conservation areas keep permitted development but add a restriction: the outdoor unit must not sit nearer to a highway bounding the property than any part of the building. In practice that pushes it to a rear or side elevation, which is usually where you would want it anyway.

Flats are covered but with tighter limits, and your lease almost certainly requires the freeholder or managing agent to approve anything fixed to the outside of the building. That consent is a separate question from planning and it catches people out far more often than the planning rules do.

Scheduled monuments are out entirely.

The noise limit is the one people trip over

42 dB(A) sounds restrictive until you understand where it is measured: at the neighbour's window, not at the unit.

A typical domestic condenser produces somewhere in the high 40s to low 50s at one metre. Sound falls away with distance, and a fence or a wall between the unit and the boundary helps further. Most positions pass comfortably. A unit bolted to a party wall directly below a neighbour's bedroom window may not.

This is a calculation, not a guess, and it is part of a proper survey.

What we do about it

We check the designation of your property at survey, before quoting. That means looking at whether you are in a conservation area, whether the building is listed, and working the noise assessment for the position we are proposing.

If an application is needed, we prepare it. If a position will not pass, we tell you before you have paid for anything rather than after.

Source: Planning Portal, planning permission for air source heat pumps, checked September 2026.

One thing coming down the line

From 28 May 2026, MCS becomes the only certification scheme recognised for the planning standard. If you are reading this after that date and comparing quotes, it is worth asking which standard an installer is working to.

If you are weighing up whether the system is worth it in the first place, the running costs are the other half of the question.

Scotland, Wales and Northern Ireland have their own rules and the limits above do not apply there.