- Planning permission isn’t usually required unless you’re in a conservation area or listed building
- Cooling-only systems aren’t covered by permitted development rules
- If in doubt, speak to your council
If you’re looking for a way to avoid the sweltering heat of yet another heatwave arriving soon, air conditioning looks awfully tempting – so much so that in the UK, portable AC units are sold out almost everywhere or going for silly money on eBay, while air con installers are booked far into the future.
With future summers expected to get even hotter, many of us are now looking into fully installed AC as a long-term investment for our homes and our health, and that means we’re likely to encounter a lot of confusion and misinformation about what you can and cannot do under UK planning and building regulations.
That confusion has been partly fuelled by social media and very misleading newspaper headlines suggesting that Net Zero-crazed councils are demanding innocent homeowners ‘RIP OUT’ their expensive installations.
The UK government’s ministry of housing, communities and local government (MHCLG) says that such coverage is incorrect. “In most cases, planning permission is not required to install [air con] for a small home if it would not materially effect the appearance of the building from outside.”
The most sensational headlines have been about air con in London and reference the London Plan, a city-specific rule that prioritises passive cooling and discourages extensive use of air con due to the heat it emits outside, which can contribute to heat islands in built-up areas.
As a spokesperson for the Mayor of London told The Telegraph: “The current London Plan does not rule out air conditioning — its policy is only applicable to major developments and requires new developments to address overheating risk from the outset — through measures such as shading, ventilation and other cooling design features.”
If you look at the detail of the newspaper stories you’ll typically find that the problem wasn’t the air con itself, but how and where it was installed.
The problem is that even the the Government’s press release above saying “Air conditioning units are not banned” also then says “However, there is no blanket rule. People should speak with their local council to check the rules, and councils should take a common-sense approach.” So that’ doesn’t exactly totally clear things up — but there are basic rules that apply broadly, which are then changed depending on the local council situation.
So here’s an overview of what rules you need to know about when you’re considering investing in permanent air conditioning, so you at least know where you’re starting from, and you can look into your area’s circumstances from there.
In this article we’ll be focusing exclusively on adding domestic air con to an existing residential home that you own. If your home is a leasehold in England you may need to obtain the freeholder’s consent in addition to the other criteria.
What kind of home you have matters
The rules depend very much on what kind of home you have. If you’re in a listed building you’ll definitely need to apply for listed building consent; if you’re in a conservation area, there will be restrictions on changing the appearance of your home, so there will be limits as to where you can place the external unit on the outside of your home.
If your home is neither listed nor in a conservation area, then the rules are largely common sense: under the rules for ‘Permitted Developments’ you don’t need planning permission provided your air con meets some reasonably straightforward technical and location criteria.
The specific criteria are similar across the UK and I’ve linked to them here:
If you’re not sure if your system meets the permitted development criteria, we’d strongly recommend a chat with 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 conditioners in the UK?
The basic rules (before you get into conversation areas, and so on) differ depending on the kind of air conditioning you’re thinking of installing.
If your air conditioner can heat as well as cool then it’s generally allowed under Permitted Development rules under their Class G permissions, which are enforced by your local council on a common-sense basis.
Provided your external condenser unit (the part of an installed air con that goes outdoors) or heat pump isn’t too big, too loud, too visible or too close to your neighbours, you don’t usually need planning permission.
That’s not the case if the air conditioner cools but doesn’t 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 permissions allow you to install air con on your property or its “curtilage”, which is the land associated with and immediately surrounding it including additional buildings. If you live in a castle the curtilage is anything inside the castle walls; if you’re in a semi-detached the curtilage usually means your garden, driveway and garage, if you have one.
Most modern air con systems are Air Source Heat Pumps (ASHP), which means they can both cool and heat the air they take in and expel.
The Class G permissions were revised in 2025 to specifically include the exterior units of ASHPs, and they 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, that also limits you to one ASHP
For a terraced, semi-detached or detached house the ASHP must not be bigger than 1.5 cubic metres. For flats the limit is 0.6 cubic metres.
A cubic metre is 1m wide, 1m tall and 1m deep. That’s bigger than a freestanding fridge: sizes differ by manufacturer and product, but as an example the outdoor units for Toshiba’s current RAS multi-split air conditioners range from 0.12m³ to 0.25m³ with the very largest model coming in at 890 x 900 x 320mm — that fits easily within the house regulations.
What kind of air conditioner can I install?
Under Class G your equipment must comply with the Microgeneration Certification Scheme, or MCS for short. The regulations are a bit odd here because while an air source heat pump must comply with the MCS, it doesn’t need to have a certificate. The details of the MCS are online here.
Where can I install my air conditioner?
The rule preventing you from installing your external unit within 1m of neighbouring properties has been scrapped. However, your installation must not negatively impact your neighbours with noise: the noise level of your external unit cannot exceed 42 decibels measured at one metre from your nearest neighbour’s front door or window. MCS-compliant units will not exceed that limit.
You can’t install the external unit on a pitched roof, or within a metre of the edge of a flat roof.
If you’re not in a conservation area or listed building, you may install the external unit on the front wall provided it’s on the ground floor.
If you’re in a conservation area you cannot install an external unit on any elevation that faces a highway.
The location of your external unit is where the common-sense criteria come in: the external unit, its cabling and any ducting must be sited in such a way that it is “so far as practicable, sited so as to minimise its effect on the external appearance of the building” and sited “so as to minimise its effect on the amenity of the area”.
If you have a wind turbine in your garden you’re out of luck: Class G doesn’t give permission for any air con installation for properties with a turbine within their curtilage.
Your air con installer will be well aware of the regulations and should be able to ensure that your air con meets all the relevant requirements, but if you have any doubts please do talk to your local council’s planning officers, because again you really don’t want them to actually have cause to force you to remove it.
What do I do to make sure there aren’t special rules in my area?
Your council will likely 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 work out whether they’d affect air con installation.
If not, or if it’s still unclear, you council will have a system for enquiries around planning permission, so you can ask if what you’re planning needs a permit without going through the process — and it means that if you need one, they can tell you exactly what’s needed.
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