Do you need planning permission for air conditioning?
Short answer for most homeowners in England: no — provided the system heats as well as cools, and you stay within a set of conditions. The rules changed significantly on 29 May 2025, and the change was firmly in your favour. But the conditions matter, a unit that only cools is treated differently, and flats, listed buildings and conservation areas each have their own wrinkles. Here's the full picture.
Beware outdated advice. Many older articles still say air conditioning always needs planning permission, or repeat the old "1 metre from the boundary" rule. Both were true before 29 May 2025 and are wrong now. Always check the date on anything you read about this — including quotes from installers working off old assumptions.
What changed in May 2025
In England, outdoor heat pump units have long been "permitted development" — allowed without a planning application if conditions are met. The catch was that the rules covered units used for heating only, which excluded air conditioning entirely. The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025, in force from 29 May 2025, rewrote this:
- Air-to-air systems that cool as well as heat are now included. Since virtually every modern split-system air conditioner is a reversible heat pump, most domestic AC installations now qualify as permitted development.
- The 1-metre boundary rule was scrapped. The outdoor unit can now sit right up against your property line — a big deal for terraced houses and small gardens where the old rule killed projects.
- The size limit for houses more than doubled, from 0.6 to 1.5 cubic metres per outdoor unit — comfortably covering almost every domestic system on the market.
- Detached houses can now have two outdoor units under permitted development; semi-detached and terraced houses are limited to one.
The official conditions are listed on the Planning Portal's air source heat pump page — treat that as the authoritative checklist.
The conditions you still have to meet
Permitted development isn't a free-for-all; it's automatic permission if every condition holds. The ones that matter in practice:
- The unit must not be used solely for cooling. A cooling-only system still needs a planning application. This rarely bites in practice — reversible units dominate the market and cost about the same — but it's the reason to specify heat/cool rather than cool-only when you buy.
- Noise compliance under the MCS 020 standard. The updated standard sets a limit of 37 dB assessed at your nearest neighbour's closest habitable window, with a formal noise assessment as part of the install. This is your installer's job — a competent F-Gas certified firm handles the calculation and paperwork as routine. From 28 May 2026, MCS 020 is the only certification route, so make sure any installer you use works to it.
- Placement rules: not on a pitched roof; if on a flat roof, at least 1 metre from the roof edge; and sited, so far as practicable, to minimise the effect on the building's appearance and the area.
- Not retrospective: the new rights apply to units installed on or after 29 May 2025. An AC unit installed without permission before that date isn't legitimised by the change.
How it breaks down by property
| Your situation | Position |
|---|---|
| House (England), reversible heat/cool unit | Usually no permission needed — permitted development if the conditions above are met |
| Detached house wanting two outdoor units | Both can be permitted development; a third needs an application |
| Flat / block of flats | Permitted development can apply to the block (one unit, 0.6 m³ limit) — but as a leaseholder you almost always need freeholder consent under your lease, which is separate from planning and usually the bigger hurdle. Full detail in our upcoming flats guide. |
| Conservation area / World Heritage Site | Permitted development can still apply, but the unit must not go on a wall or roof fronting a highway — in practice, rear elevation only |
| Listed building or its grounds | No permitted development — you'll need consent; talk to your local authority before committing to anything |
| Cooling-only unit (any property) | Needs a planning application |
| Wales, Scotland, Northern Ireland | The May 2025 changes apply to England only. The devolved nations have their own permitted development regimes — check with your local authority or ask your installer |
Two traps worth knowing about
Article 4 directions and planning conditions. Councils can remove permitted development rights for specific streets or estates, and some new-build homes have planning conditions doing the same. It's uncommon, but a two-minute check with your local planning authority (or a question to your installer, who'll know the local patch) rules it out.
Old quotes and old advice. If an installer tells you the unit must be a metre from the fence, or that AC can't be permitted development at all, they're working from the pre-2025 rules. It's a useful screening question, in fact — a firm that knows the current rules and mentions the MCS 020 noise assessment unprompted is a firm keeping up with its obligations.
What to actually do
For a normal house in England: get quotes for a reversible (heat/cool) split system from F-Gas certified installers, and confirm in writing that the installation will comply with permitted development conditions including the MCS 020 noise assessment. The installer handles the rest — there's no form for you to file, because permitted development is the permission. Keep the paperwork (noise assessment, commissioning certificate) in case you sell the house or a neighbour ever asks.
For flats, listed buildings or conservation areas: have the conversation with your freeholder or local authority before getting survey-stage quotes, so you're not designing a system you can't install.
Ready to move? Get up to three free quotes from certified installers — mention your property type and any conservation-area status in the form so they price and site it correctly first time. Not sure what size system you need? Two minutes in the calculator answers that.
Quick answers
Does a portable air conditioner need planning permission?
No — never. Portables are appliances, not development. Nothing is fixed to the building, so planning rules don't apply. If planning is a blocker for you, a portable is the zero-permission fallback.
Can my neighbour object to my air conditioning unit?
If your installation meets all permitted development conditions, it's lawful and there's no application for a neighbour to object to. The noise standard exists precisely to protect neighbours — which is why keeping the MCS 020 assessment on file is worthwhile if relations ever sour.
Do I need permission to replace an existing unit?
Replacement is covered by the same permitted development right, subject to the same conditions — the replacement unit must also stay within the size limit and noise standard.
What happens if I install without meeting the conditions?
If any condition is breached, the whole installation falls outside permitted development and the council can require a retrospective planning application — or, if refused, removal. It's cheap insurance to have your installer confirm compliance in writing before work starts.