Do you need planning permission for air conditioning?
A cooling-only unit usually needs full planning permission in England, while a reverse-cycle (heat and cool) unit is often permitted development. Here are the rules, the conditions and the exceptions.
In England, a cooling-only air conditioning unit generally needs full planning permission, while a reverse-cycle unit (an air-to-air heat pump that both heats and cools) can usually be installed under permitted development, subject to conditions. This is the one fact most pages get wrong, so it is worth being clear about up front.
The reason is that outdoor air conditioning units are treated as air source heat pumps for planning. The permitted development right that covers them only applies where the unit is not used solely for cooling. So if your system can heat as well as cool, you are likely covered without a planning application, as long as it meets the conditions below. If it only cools, you will probably need to apply.
This guide explains the rules in plain English: the conditions a permitted-development install must meet, the noise test at your neighbour's window, what changed in May 2025, and the exceptions for flats, listed buildings and conservation areas. Scotland, Wales and Northern Ireland have their own rules, covered near the end.
This is general guidance, not legal or planning advice. Planning law is detailed and fact-specific, and it changes. Always check the gov.uk planning permission guidance and your local planning authority, and use a qualified installer before you proceed.
The short answer: cooling-only vs reverse-cycle
The decisive question is whether your unit heats as well as cools.
Reverse-cycle (heat and cool): usually permitted development in England, provided it meets the Class G conditions below. No planning application needed in most cases.
Cooling-only (no heating mode): generally needs full planning permission, because it falls outside the permitted-development right.
This split exists because there is no separate "air conditioning" category in planning law. Outdoor units run through Class G of Part 14 of the General Permitted Development Order, which is the air source heat pump class. A condition inserted on 29 May 2025 means the right only applies where the unit "is not solely used for the purpose of cooling". A reverse-cycle unit that heats and cools clears that condition; a cooling-only condenser does not.
The Planning Portal puts it the same way: the rights only apply if the system provides a heating function (including a system that does both heating and cooling). If it offers a cooling function only, the rights do not apply and a planning application is required.
Why air con planning runs through the "heat pump" rules
A reverse-cycle air conditioner and an air-to-air heat pump are the same machine. It moves heat rather than generating it, so in summer it pushes heat out of your home (cooling) and in winter it pulls heat in (heating). Because the planning system classes these as air source heat pumps, the permitted development right for heat pumps is the right that decides whether you can skip a planning application.
The planning question is almost always about the outdoor condenser unit on a wall, roof or the ground. The indoor unit is rarely the issue. So when you read the conditions below, picture the box outside.
The conditions a permitted-development install must meet
For a reverse-cycle unit on a house in England to qualify as permitted development, the install has to satisfy all of the Class G conditions. In plain English:
It must heat, not just cool. The unit must not be used solely for cooling.
Noise. It must comply with the MCS Planning Standard (MCS 020). The predicted sound level at the nearest neighbour's habitable-room window must not exceed 42 dB(A). Above that, a full planning application is required.
Number of units. Up to two units on or within the grounds of a detached house, or one unit on a semi-detached or terraced house.
Volume. The outdoor unit, including any housing, must not exceed 1.5 m³ on a house.
Siting. Not on a pitched roof; if on a flat roof, not within 1 metre of the roof edge. It should be sited to minimise its effect on the look of the building and on neighbours, and removed when no longer needed.
| Condition | Reverse-cycle unit on a house |
|---|---|
| Heating function | Required (must not be solely for cooling) |
| Noise at neighbour's window | Max 37 dB(A) under MCS 020(a) |
| Number of units | Up to 2 (detached); 1 (semi or terraced) |
| Outdoor unit volume | Max 1.5 m³ |
| Roof siting | Not on a pitched roof; 1 m clear of a flat-roof edge |
Most domestic single-split condensers sit well under 1.5 m³, so volume is rarely the sticking point. In practice the binding constraints are usually the cooling-only rule, the noise test, siting, and whether the property is listed or in a conservation area.
What changed in May 2025
On 29 May 2025 the rules were relaxed in England (S.I. 2025/560), which made permitted development easier for many homes:
The 1 metre boundary rule was removed. A ground-sited unit can now be placed closer than 1 metre to the property boundary.
The volume limit was raised from 0.6 m³ to 1.5 m³ for a house (it remains 0.6 m³ for a block of flats).
More units are allowed: up to two on a detached house, and one on a non-detached house (semi or terraced) or a block of flats.
The same set of changes brought in the cooling-only condition, so these relaxations and the heating requirement arrived together.
The noise rule: MCS 020(a) and the 37 dB(A) test
Noise is the most common reason an otherwise compliant install fails to qualify as permitted development. Under MCS 020(a) (the MCS Planning Standard), the installer calculates the predicted sound and checks the level 1 m from the centre of the nearest neighbour's habitable-room window or door. If it does not exceed 37 dB(A), the install can be permitted development on the noise condition. If it does, you need a full planning application.
Compliance with the updated MCS 020 became mandatory for permitted-development heat pump and air con installs in England from 20 September 2025. A good installer will run this calculation as part of the job and advise on siting to keep the unit within the limit, which is one reason it pays to use someone who handles approvals. Since 28 May 2026 the tightened MCS 020(a) has been the only accepted scheme, and its 37 dB limit (measured as a 5-minute LAeq) replaces the older 42 dB(A) ceiling. The figure is a calculated level at the neighbour's window, not the number on the unit's spec sheet.
Listed buildings and conservation areas
Two situations need extra care, and one removes permitted development entirely.
Listed buildings. Permitted development does not apply. You will need listed building consent for an external unit, and likely planning permission too. Always check before any work.
Conservation areas and World Heritage Sites. The unit must not be on a wall or roof that fronts a highway, nor nearer to a bounding highway than the nearest part of the house. In practice, many conservation-area installs still need permission.
Article 4 directions. A local authority can issue an Article 4 direction that withdraws permitted development rights in a specific area, which means a planning application is required even for an install that would normally be permitted. Your local planning authority can tell you if one applies.
Scheduled monuments. Permitted development does not apply.
Flats and maisonettes: what's different
Flats face tighter limits than houses. On a block of flats the outdoor unit volume limit is 0.6 m³, not the 1.5 m³ allowed on a house, and only one unit is permitted. The same heating requirement, noise test and siting conditions apply. If you do not own the building or the external wall outright, you will usually also need the freeholder's or management company's consent, separate from planning. Check your lease as well as your local planning authority.
Scotland, Wales and Northern Ireland
Permitted development is devolved, so the rules differ outside England. Treat the following as a starting point and confirm your own position with the relevant authority.
Wales. There is an air source heat pump permitted development right, but it is tighter than England. Commonly cited limits include the unit being used solely for heating, an outdoor volume not exceeding 1 m³, and no part within 3 metres of the boundary. Conservation-area and listed-building restrictions apply.
Scotland. Scotland has its own permitted development rules. Heat pumps are often permitted development but with conditions, such as siting away from the principal elevation or road frontage, and different rules in designated areas.
Northern Ireland. Northern Ireland has a separate planning regime. Heat pump permitted development has applied since around 2023, with conditions reported to include a setback from the neighbour boundary and noise limits.
Whichever nation you are in, always check your local planning authority before you commit.
Building Regulations and F-Gas: the approvals that always apply
Planning permission is not the only approval to think about. These apply regardless of whether you need a planning application.
Building Regulations. Electrical work for an air con unit is notifiable under Part P, and overheating and energy-efficiency rules can be relevant. Using an installer registered with MCS or a relevant Competent Person Scheme keeps this straightforward.
F-Gas. The refrigerant circuit must be installed by an F-Gas (REFCOM) certified engineer. F-Gas is the regulation covering fluorinated refrigerant gases, and this is a legal requirement separate from planning. A cheap quote from someone without certification is a false economy, and often an illegal one.
Is there a grant? The £2,500 air-to-air Boiler Upgrade Scheme
For a long time the Boiler Upgrade Scheme excluded typical air conditioning. That changed from 28 April 2026, when an air-to-air heat pump grant of £2,500 became an approved grant category in England and Wales. This is separate from, and lower than, the £7,500 grant for air-to-water heat pumps and ground source.
The detail matters, so read this carefully rather than assuming free air con:
It applies to reverse-cycle units that heat and cool (air-to-air heat pumps), installed by an MCS-certified installer.
It is aimed at units replacing an existing fossil-fuel or electric heating system, not comfort cooling bolted on alongside a retained gas boiler.
It does not cover portable units.
It is England and Wales only. Scotland (Home Energy Scotland support applies instead) and Northern Ireland are not covered by the Boiler Upgrade Scheme.
The £2,500 air-to-air grant has been live since 28 April 2026 and now appears on the consumer-facing GOV.UK "What you can get" page. Check GOV.UK and Ofgem for the current conditions before relying on it.
What happens if you install without permission
If you install a cooling-only unit, or an install that breaches the conditions, without the planning permission it needed, your local planning authority can take enforcement action. You may be required to apply retrospectively for permission, or to remove the unit if permission is refused. A retrospective application is no more likely to succeed than one made in advance, so it is cheaper and far less stressful to check first. A householder planning application in England is £548 (the fee from 1 April 2026, and it is uprated each April), plus a Planning Portal service charge of £75.83 + VAT if you apply online. That is still far cheaper than removing an installed unit and reapplying. Fees were correct at July 2026 — check the current figure before you apply.
How to check and apply
A sensible order of play:
1. Decide heating or cooling-only. If you want the unit to qualify as permitted development, choose a reverse-cycle (heat and cool) system.
2. Check designations. Confirm whether your home is listed, in a conservation area, or covered by an Article 4 direction. Your local planning authority will know.
3. Get a noise assessment. A reputable installer will run the MCS 020 calculation and advise on siting before committing.
4. Apply if needed. Where a planning application or listed building consent is required, the Planning Portal is the route.
A good installer can manage the noise assessment and any application for you, which is the simplest way to avoid a costly mistake. For what the job itself involves, including where the outdoor unit goes, see our guide to how air conditioning is installed.
Frequently asked questions
Do you need planning permission for air conditioning in the UK? +
It depends on the unit and where you live. In England, a cooling-only unit usually needs full planning permission, while a reverse-cycle unit that heats and cools is often permitted development if it meets the conditions on noise, number, volume and siting. Scotland, Wales and Northern Ireland have their own rules. Always check your local planning authority.
Does a cooling-only air con unit need planning permission? +
In England, generally yes. The permitted development right only applies where the unit is not used solely for cooling, so a cooling-only condenser falls outside it and a planning application is normally required.
Do I need planning permission for multiple air conditioning units? +
Permitted development allows up to two units on a detached house, or one on a semi-detached or terraced house or a block of flats. More than that, and the extra units would need planning permission.
Do you need planning permission for air con in a conservation area or on a listed building? +
Listed buildings always need listed building consent, and permitted development does not apply. In a conservation area, the unit must not face a highway and many installs still need permission. Check your local planning authority before any work.
Do you need planning permission for an external condenser on a flat? +
Flats have tighter limits: a 0.6 m³ volume cap and only one unit on the block, with the same heating, noise and siting conditions. You will usually also need the freeholder's or management company's consent. Check your lease and your local planning authority.
Is it illegal to install an air conditioner in the UK? +
No. Home air conditioning is legal. You may need planning permission depending on the unit and location, the refrigerant work must be done by an F-Gas certified engineer, and the electrical work is notifiable, but installing a properly fitted, compliant system is entirely lawful.
Getting the installation right
A compliant install means the noise assessment, F-Gas refrigerant work and notifiable electrics are all handled properly. Our installation guides walk through what a good job looks like.
Rules and figures correct as of July 2026. Planning law and grant terms change, so confirm the current position with your local planning authority and on GOV.UK before proceeding.
For related reading, see how much air conditioning costs to weigh the price of going through planning, our guide to choosing an air conditioning system where the heat-and-cool decision now has a direct planning consequence, and wall-mounted split systems if you are deciding on a unit.
