Air Conditioning Planning Permission UK
Most domestic air conditioning installations in England don't need a planning application — they fall under permitted development, within conditions. But conservation areas, listed buildings, flats and noise rules catch people out. Here's the practical guidance, in plain English.
Permitted development: the general rules for houses
In England, the outdoor unit of a domestic air source system is usually treated as permitted development — no planning application needed — provided conditions along these lines are met. Presented as general guidance; the precise wording sits in the planning legislation and your council's interpretation:
- Up to two outdoor units on a detached house (one on other house types) under permitted development — the cap was raised from one in the 2025 reform.
- Size limit — the unit's outdoor compressor box must be within the volume limit, raised from 0.6 m³ to 1.5 m³ in England on 29 May 2025, which now covers virtually every domestic outdoor unit.
- No minimum distance from the boundary — the old 1 m boundary rule was scrapped in England on 29 May 2025, so a unit can sit close to a fence, though sensible siting and the noise limit below still apply.
- Not on a pitched roof, and positioned to minimise visual impact — avoiding a front wall facing a highway is the safe course.
- Below specified height limits if wall-mounted or on a flat roof.
- Heating as well as cooling — since 29 May 2025 the rights explicitly cover air-to-air heat pumps that also cool, which is nearly all air conditioning; a cooling-only system that cannot heat still needs a planning application.
- Noise conditions — installations are expected to meet sound-level standards at the nearest neighbouring window (see the noise section below).
Important: permitted development rights differ in Wales, Scotland and Northern Ireland, can be removed by Article 4 directions or conditions on your estate, and are interpreted locally. Always confirm with your local planning authority before installing — a short email with the siting plan is usually enough.
Conservation areas and listed buildings
In a conservation area, permitted development is more restricted — outdoor units visible from the street are commonly refused, and siting on rear or side elevations, at ground level and screened, is the practical route. On a listed building, the bar is higher again: listed building consent is required for works affecting character, which realistically includes fixing an outdoor unit, drilling pipework through historic fabric and external trunking. Neither situation makes air conditioning impossible — sensitive siting, acoustic enclosures and careful routing get schemes approved regularly — but apply first, never retrofit and hope. Fines and enforced removal are real outcomes for unauthorised works to listed buildings.
Flats, leaseholds and rented homes
Planning permission and permission-from-the-freeholder are different hurdles, and flats usually need both. Fixing an outdoor unit to a block's external wall almost always requires freeholder or management-company consent under the lease, and flats don't enjoy the same permitted development rights as houses, so a planning application is often needed too. Tenants need the landlord's written consent regardless of tenure. Start these conversations before getting quotes finalised — a good engineer can supply the spec sheets and noise data the freeholder will ask for.
Noise limits and MCS 020-style assessments
The noise condition attached to permitted development for air source units is assessed with a standard methodology (the MCS 020 planning-standard calculation), which combines the unit's sound power, distance to the nearest neighbouring habitable-room window, and screening from barriers. The pass mark is 37 dB(A) or lower at the nearest neighbouring habitable-room window, and from 28 May 2026 the assessment must use the updated MCS 020a standard. In practice: modern inverter outdoor units are quiet, and most sensible sitings pass comfortably — but a unit tight against a boundary fence pointing at a neighbour's bedroom window may not. Your installer should run this assessment as part of the survey; ask to see it. Keeping the unit off shared walls, on anti-vibration mounts, and away from bedroom windows is good practice whatever the paperwork says.
Commercial planning notes
Commercial installations sit outside householder permitted development. Small condensers to the rear of a shop may be uncontroversial, but units visible from the street, on shopfronts, in conservation areas or on flats-above-shops frequently need planning permission, and landlord consent under a commercial lease is near-universal. Larger plant (VRF condensers, roof-mounted units) may also engage noise conditions and, for tenanted buildings, licence-to-alter processes. Factor the lead time into project planning — see our commercial cost guide for budgets.
Before you book an installation
- House in England, up to two units on a detached home (one otherwise), each within 1.5 m³, rear or side wall, sensible low-level siting → usually permitted development since the 2025 reform that scrapped the 1 m boundary rule, but confirm with your council.
- Conservation area or listed building → contact the planning authority first; expect to apply.
- Flat or leasehold → freeholder consent plus likely planning application.
- Renting → landlord's written consent.
- Any doubt → a Lawful Development Certificate from your council gives formal confirmation for modest cost and is worth having when you sell.
Disclaimer: this guide is general information, not legal or planning advice. Rules change and are applied locally — always verify your specific installation with your local planning authority before work begins.
Frequently asked questions
Sources & methodology
- Permitted development conditions summarised from UK planning guidance for domestic air source units, as at 2026.
- Noise-assessment methodology per the MCS 020 planning standard.
- This page is general guidance, not planning advice; confirm requirements with your local planning authority.
Get engineers who handle the paperwork properly
Air Con Surrey is a free matching service — the vetted, F-Gas certified engineers we match you with survey siting, run noise assessments and advise on consent before anything is drilled.