- Planning permission is not normally required unless you are in a conservation area or listed building
- Cooling systems are not covered by permitted development rules
- If in doubt, talk to your council
If you’re looking for a way to avoid the stifling heat of another soon-to-arrive heatwave, air conditioning is looking very tempting – so much so that portable AC units in the UK are sold out almost everywhere or go for silly money on eBay, while aircon installers are booked far into the future.
With future summers expected to be even hotter, many of us are now looking at fully installed AC as a long-term investment for our homes and our health, which means we’re likely to encounter a lot of confusion and misinformation about what you can and can’t do under UK planning and building regulations.
This confusion has been fueled in part by social media and highly misleading newspaper headlines suggesting that Net Zero-mad councils are demanding innocent homeowners ‘RIP OUT’ their expensive installations.
The UK government’s Department for Housing, Communities and Local Government (MHCLG) says such cover is wrong. “In most cases, planning permission is not required to install [air con] for a small home if it would not significantly affect the appearance of the building from the outside.”
The most sensational headlines have been about air conditioning in London, referring to the London Plan, a city-specific rule that prioritizes passive cooling and discourages extensive use of air conditioning because of the heat it emits outside, which can contribute to heating islands in built-up areas.
As a spokesman for the Mayor of London told The Telegraph: “The current London Plan does not rule out air conditioning – its policy only applies to larger developments and requires new developments to address the risk of overheating from the outset – through measures such as shading, ventilation and other cooling design features.”
If you look at the details in the newspaper stories, you will typically find that the problem was not the air conditioner itself, but how and where it was installed.
The problem is that even the government press release above, which says “Air conditioning is not banned”, also then says “However, there is no blanket rule. People should speak to their local council to check the rules, and councils should take a common sense approach.” So that doesn’t quite clear things up – but there is basic rules that apply broadly, which are then changed depending on the local council’s situation.
So here’s an overview of what rules you need to know when you’re considering investing in permanent air conditioning, so you at least know where to start and you can take a closer look at your area’s conditions from there.
In this article, we will focus exclusively on adding residential air conditioning to an existing residential home that you own. If your home is a tenancy in England, you may need to obtain the owner’s consent in addition to the other criteria.
What kind of home you have matters
The rules largely depend on the type of home you have. If you are in a listed building you will definitely need to apply for listed building permission; if you are in one protected areathere will be restrictions on changing the look of your home, so there will be limits to where you can place the outdoor unit on the outside of your home.
If your home is neither protected nor in a protected areathen the rules are pretty much common sense: under the rules for ‘Permitted developments’ you do not need planning permission provided your air conditioner meets some fairly simple technical and location criteria.
The specific criteria are the same across the UK and I have linked them here:
If you are unsure whether your scheme meets the permitted development criteria, we would strongly recommend speaking to your local council’s planning department: get it wrong and the council can make you remove the system at your own expense. You don’t want to make what could be a very expensive mistake.
What are the core rules for home air conditioning in the UK?
The ground rules (before entering conversation areas and so on) vary depending on the type of air conditioning you are considering installing.
If your air conditioner can hot as well as cool so it is generally permitted under the Permitted Development Rules under their Class G Permitswhich is enforced by your local council on the basis of common sense.
Assuming your external condenser unit (the part of an installed air conditioner that goes outdoors) or heat pump is not too big, too tall, too visible or too close to your neighbours, you usually do not need planning permission.
It is not the case if the air conditioner cools but does not also have a heating element. You need planning permission for that and councils are keen to discourage such installations.
How big can your aircon be in the UK?
The Class G permits allow you to install air conditioning on your property or its “enclosure”, which is the land connected to and immediately surrounding it, including additional buildings. If you live in a castle, the enclosure is everything within the castle walls; if you’re in a semi-detached house, the screening usually means your garden, driveway and garage if you have one.
Most modern air conditioners are Air Source Heat Pumps (ASHP), which means they can both cool and heat the air they take in and exhaust.
The Class G permits were revised in 2025 to specifically include the external units of ASHPs and state that in a permitted development:
- You can have up to two ASHPs on a detached house or bungalow
- If you live in a semi-detached or terraced house, you may only have one ASHP
- If you live in a block of two flats or more, it also limits you to one ASHP
For one terraced, semi-detached or semi-detached house ASHP must not be larger than 1.5 cubic meters. Before apartments, the limit is 0.6 cubic metres.
A cubic meter is 1 m wide, 1 m high and 1 m deep. It’s bigger than a freestanding fridge: sizes vary by manufacturer and product, but as an example, the outdoor units for Toshiba’s current RAS multi-split air conditioners range from 0.12 m³ to 0.25 m³ with the largest model measuring 890 x 900 x 320 mm – it easily fits within house rules.
What kind of air conditioner can I install?
Under class G your equipment must comply with the Microgeneration Certification Schemeor MCS for short. The rules are a little strange here, because while an air source heat pump must comply with MCS, it does not need to have a certificate. The details of MCS are online here.
Where can I install my air conditioning system?
The rule preventing you from installing your external device within 1m of neighboring properties has been scrapped. However, your installation must not adversely affect your neighbors with noise: the noise level of your external device must not exceed 42 decibels measured one meter from your nearest neighbour’s front door or window. MCS-compliant devices will not exceed this limit.
You cannot install the external unit on a pitched roof or within one meter of the edge of a flat roof.
If you are not in a listed area or listed building, you must can install the external unit on the front wall, provided it is on the ground floor.
If you are in a conservation area, you cannot install an external device on any elevation facing a highway.
The location of your external device is where the common sense criteria come into play: the external device, its cables and any ductwork must be located in such a way that it “is, as far as practicable, located so as to minimize its impact on the external appearance of the building” and located “to minimize its impact on the amenity of the area”.
If you have a wind turbine in your garden, you are out of luck: Class G does not permit any air conditioning installation for properties with a turbine within their enclosure.
Your air conditioning installer will be very familiar with the regulations and should be able to ensure that your air conditioning meets all the relevant requirements, but if in doubt speak to your council’s planning officer, as again you really don’t want them to have any reason to actually force you to remove it.
What do I do to make sure there are no special rules in my area?
Your council will probably have a whole website dedicated to helping with planning information, including potentially a map showing whether your home is included in any conservation areas and what the specific orders around those areas are, so you can find out if they will affect the installation of air conditioning.
If not, or if it’s still unclear, your council will have a planning permission inquiry system, so you can ask if what you’re planning needs a permit without going through the process – meaning that if you do need one, they can tell you exactly what’s needed.
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