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Permitted development checker for AC and heat pumps

Check an outdoor AC or heat pump unit against the permitted-development limits for England, including conservation areas and listed buildings.

Where is the home?

What is the unit?

This is the question that decides the route since 29 May 2025.

Type of home

Listed building?

Conservation area?

Article 4 direction?

Where will the outdoor unit go?

Does that wall or roof face a road?

m³

Width x height x depth in metres. A typical 3.5 kW unit is about 0.8 x 0.6 x 0.3 = 0.14 m³.

Outdoor units in total

1

MCS 020 a) noise test

37 dB(A) or less at every neighbouring window or door.

Work it out with the noise checker

Possibly permitted development, once you confirm a few things

What to confirm

  • Whether the building is listed changes the answer. Search the National Heritage List for England before you go further.
  • Councils can remove the right with an Article 4 direction. Your council can tell you if one applies.
  • Conservation areas tighten the rules. Your council lists its conservation areas online.
  • It must pass the MCS 020 a) sound test: 37.0 dB(A) or less at every neighbouring window or door. Use the noise checker.

What already fits the rules

  • It heats as well as cools, so it can use the Class G permitted-development right for air source heat pumps.
  • It is a house, which holds the Class G right directly.
  • The outdoor unit is within the 1.5 cubic metre size limit.
  • 1 outdoor unit is within the limit.

An indicative summary of England's permitted-development rules, not legal advice. Confirm the final position with your local planning authority before installing.

How this works

The checker applies England's permitted-development rules for air source heat pumps, Class G of Part 14 of the General Permitted Development Order 2015, as amended by SI 2025/560 from 29 May 2025. That amendment changed the key condition to “not solely used for the purpose of cooling”, so an air-to-air heat pump that also heats can be permitted development on a house, and a cooling-only unit cannot.

It then checks the siting and size limits (up to 1.5 cubic metres on a house, 0.6 on a block of flats; up to two units on a detached house, otherwise one; not on a pitched roof; at least 1 metre from the edge of a flat roof; not on an upper wall facing a road; not facing a road in a conservation area), listed-building status, Article 4 directions and the MCS 020 a) noise test. Anything you are unsure about is treated as a question to confirm, never as a pass.

This is an indicative summary of England permitted-development rules for outdoor units, not legal advice. Rules change and vary locally - confirm the final position with your Local Planning Authority before installing.

Sources

Questions people ask

Does air conditioning need planning permission in England?

A cooling-only unit does, because since 29 May 2025 only a unit that also heats can use the permitted-development right. An air-to-air heat pump can be permitted development on a house within the limits.

Can I fit an outdoor unit on the front of my house?

On a wall above ground floor that faces a road, no. In a conservation area, no wall or roof facing a road. Ground-floor front walls outside conservation areas can be possible within the other limits.

Is there still a 1 metre boundary rule?

No. The 2025 amendment removed it. Noise now does that job through the MCS 020 a) test at neighbouring windows and doors.