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Planning permission for an outdoor air conditioner

Updated: 21 October 2026

An installer has told you the outdoor unit for a three-room system does not need planning permission. That sentence is sometimes true in England, and it is often too broad. Planning permission for air conditioning in the UK depends on the nation, on whether the unit can heat, on how many boxes you add, and on the size of each one. Building regulations are a second approval. This page is for a householder in England or Scotland siting one outdoor unit. It is not legal advice. The equipment is on the [triple split air conditioner comparison](/hub/cooling/triple-split-air-conditioner). Peter F. used legislation.gov.uk, the Planning Portal and GOV.UK on 20 October 2026. A qualifying purchase can earn a commission at no extra cost to you.

An installer has told you the outdoor unit for a three-room system does not need planning permission. That sentence is sometimes true in England, and it is often too broad.

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On this page
  1. 1.England, Class G
  2. 2.Scotland is heating or hot water only
  3. 3.Building regulations and noise are separate
  4. 4.Before the installer drills

England, Class G

In England the relevant permitted-development class is Class G of the General Permitted Development Order, as amended. The Planning Portal’s householder note says the rights apply when the system provides heating, including a unit that both heats and cools. A cooling-only air conditioner needs an application. SI 2025/560 says the unit must not be used solely for cooling. The outdoor unit must stay within 1.5 cubic metres for a house and 0.6 cubic metres for a flat. One unit is the count on a non-detached house and on flats. A detached house may go to two. That layout choice is on the multi split vs three single splits page. Measure the outdoor unit on the manufacturer’s drawing. These three amazon.co.uk listings do not give that volume.

Scotland is heating or hot water only

Scotland does not use England’s sentence. Class 6H allows one air source heat pump for domestic heating or hot water only. A cooling function does not sit inside that sentence. If the triple split is there to cool bedrooms in July, do not assume England’s heat-and-cool line applies. The right does not cover a unit in the curtilage of a listed building or in a World Heritage Site. In a conservation area the circular’s position is a rear, ground-floor siting. A second outdoor unit is outside that right. Use the council’s address, not the installer’s van, and ask which class they are relying on, in writing, before they drill.
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Building regulations and noise are separate

Planning permission and building regulations are different gates. GOV.UK lists fixed air conditioning among work that can need building-regulations approval. You can be inside Class G and still need building control for the fixed system and for a new circuit. A new circuit is notifiable unless a competent person certifies it. An installer who says no planning has not answered who notifies building control. Noise is a third gate. MCS 020a supports a permitted-development claim. Passing a worksheet does not stop a neighbour complaining, and it is not a defence if the council later decides the noise is a statutory nuisance. Breaching a home abatement notice can mean a fine of up to £5,000. The 20 dB line on these listings is not a planning noise result. Do not put it on an application form.

Before the installer drills

Email the council before the bracket goes on, even when you think Class G or Class 6H applies. Describe one outdoor unit, say whether it heats as well as cools, give the volume from the manufacturer’s sheet, and say if the building is listed, in a conservation area, or a flat. Keep the reply. A leasehold flat needs the freeholder as well. The 0.6 cubic metre English limit and a lease that bans external plant can both stop the job. Book an F-gas certified firm for the pipes. Permitted development is not a licence to joint refrigerant. Labels and combination data are on the triple split air conditioner buying guide. How you run the system after commissioning is on the how to use a multi split air conditioner page. Pay the deposit after the council note, the lease, the building-control route and the F-gas firm are named.

Common questions

Do I need planning permission for an outdoor air-conditioning unit?
Sometimes. In England a heat pump that is not used solely for cooling can be permitted development if every Class G test is met, including MCS standards, volume and the unit count. Cooling-only needs an application. In Scotland Class 6H is heating or hot water only. Ask your own council. This article cannot clear your wall.
What if it is cooling only?
In England, apply. The Planning Portal says cooling-only air conditioning is outside the permitted-development right, and Class G says the unit must not be used solely for cooling. In Scotland the class is heating or hot water only, so cooling-only fails there for a different sentence. A heat-pump sticker does not help if the quote describes cooling alone.
Is the Scottish rule the same?
No. England can allow a unit that both heats and cools if the other Class G tests pass. Scotland’s Class 6H is domestic heating or hot water only, and it allows one air source heat pump. Circular 1/2024 adds tighter place rules, including listed curtilage, World Heritage Sites and a rear ground-floor limit in conservation areas.
How many outdoor units can I have without an application?
In England, Class G blocks more than one unit on a non-detached house and on flats, and more than two on a detached house, and only when the rest of the class is met. Scotland’s right is one air source heat pump. Three mono-split condensers exceed both counts. One triple-split outdoor unit can still fail the heating, volume or heritage tests.
Is building regulations the same as planning?
No. You can have permitted development and still need building-regulations approval for a fixed air conditioner. A new circuit is notifiable unless a competent person certifies it. Planning answers where the box may stand. Building control answers how the fixed system and the wiring are signed off.
Can a neighbour still complain if the unit met the noise worksheet?
Yes. MCS 020a supports a permitted-development claim. It does not stop the council investigating a statutory nuisance afterwards. A home abatement notice that is ignored can lead to a fine of up to £5,000. Do not quote a bare 20 dB listing figure as the boundary noise.

Related pages

Best triple split air conditioner

Triple split air conditioner

Buying a triple split air conditioner for three rooms

How to use a multi split air conditioner in the UK

Multi split vs three single splits: one wall or three

Sources

Public UK sources named below. amazon.co.uk prices, stars and review counts on these listings were read on 19 October 2026. Page updated 20 October 2026.

  1. GOV.UK F-gas company certification (retrieved 2026-10-20)
  2. GOV.UK F-gas qualifications (retrieved 2026-10-20)
  3. REFCOM pre-charged splits (retrieved 2026-10-20)
  4. England Class G (retrieved 2026-10-20)
  5. Planning Portal (retrieved 2026-10-20)
  6. Scotland Class 6H (retrieved 2026-10-20)
  7. GOV.UK building regulations (retrieved 2026-10-20)
  8. Energy label classes (retrieved 2026-10-20)