Do I need planning permission for air conditioning?
The permitted development rules, what they actually say, and the one clause that decides whether your install needs an application.
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The short answer
In most cases, no. Air conditioning that also heats counts as an air source heat pump, and installing one on a house or a block of flats is permitted development in England, so no planning application is needed as long as the limits are met. The catch is a condition in the rules: the unit must not be used solely for cooling. A cooling only system falls outside permitted development. Every system we install is a reversible heat pump that heats as well as cools, so it stays inside the rules. Permitted development does not apply at all to listed buildings or scheduled monuments, and it is restricted where an Article 4 direction is in force.
Why air conditioning counts as a heat pump
The rules that matter live in Class G of Part 14 of the General Permitted Development Order, the part covering microgeneration. Class G is written about air source heat pumps, not about air conditioning, and that wording is what confuses most of the advice you will find online.
A modern wall mounted split system is an air source heat pump. It moves heat rather than making it, and it runs the cycle in both directions: out of the room in summer, into the room in winter. That is why the same box does both jobs, and it is why the rules treat it as a heat pump rather than as something separate.
So the question is not really whether air conditioning needs permission. It is whether your installation meets the Class G limits.
The clause almost every other page gets wrong
Class G permits the installation on the condition that the heat pump is not solely used for the purpose of cooling. A unit that only cools does not qualify, and installing one would need a planning application. Every range we fit heats and cools, which is what keeps a standard install inside permitted development.
The limits your install has to meet
All of these apply to a normal domestic installation in England. Miss one and the permitted development right falls away, which means an application rather than an automatic no.
Size of the outdoor unit
The outdoor unit, including its housing, must not exceed 1.5 cubic metres on a house. On a block of flats the limit is tighter, at 0.6 cubic metres. A domestic wall mounted system sits comfortably inside both, and we confirm the actual figure for the unit going on your wall at the survey.
How many units
On a detached house the first two air source heat pumps are permitted development. On any other house, and on a block of flats, only the first one is. A second unit on a semi or a terrace is where a lot of multi room jobs quietly stop being permitted development, so it is worth knowing before you plan room two.
Where it can go
Not on a pitched roof, ever. On a flat roof it has to sit at least one metre in from the external edge. Elsewhere it must not go on any part of a wall above ground floor level if that wall fronts a highway.
The standard it has to meet
The installation has to comply with the MCS planning standard, MCS 020a, which is the document setting out how the unit is positioned and assessed. A competent installer works to it as a matter of course.
Taking it away again
The rules require the unit to be removed as soon as reasonably practicable once it is no longer needed. It rarely matters while you live there, and it occasionally matters at sale.
When you do need to apply
These are the situations where permitted development either does not apply or is cut back, and where the answer is a planning application rather than a judgement call.
Listed buildings and scheduled monuments
Permitted development rights do not apply within the curtilage of a listed building or on a scheduled monument. That is a firm no rather than a maybe, and listed building consent is a separate consideration on top of planning permission.
Conservation areas and World Heritage Sites
Permitted development survives, but with an extra restriction: the unit must not be installed on a wall or a roof that fronts a highway, or nearer to a bounding highway than the nearest part of the building itself. In practice that usually means the condenser goes round the back, which is where we would want to put it anyway.
Where an Article 4 direction is in force
A council can remove permitted development rights across a defined area with an Article 4 direction. Where one applies, you apply for permission for work that would otherwise have been automatic. They are local and specific, so the only reliable check is your council's own map.
Flats, and the separate question of your lease
Planning and your lease are two different permissions and you can need both. Even where an installation is permitted development, a leaseholder usually needs the freeholder's written consent to fix anything to an external wall or to put a unit on a balcony. That consent takes longer to get than most people expect, so it is worth starting early.
Anything that is not a home
Class G is about dwellinghouses and blocks of flats. An installation on non domestic premises falls outside it and is likely to need an application.
What changed recently
Two changes are worth knowing, because a lot of the advice still online reflects the rules before them. The requirement that a unit sit at least one metre from the property boundary was removed in England on 29 May 2025, which opened up narrow side returns that previously ruled themselves out. And the volume allowance on a house rose to 1.5 cubic metres, which is well beyond what a domestic split system needs.
The practical effect is that fewer London installs need an application now than did a couple of years ago, particularly on terraces and semis where the only sensible condenser position was close to a fence.
How we handle it
We work out where the outdoor unit goes at the free survey, and where the answer touches any of the above we say so then, rather than on the day of the install. If your property is listed, in a conservation area, or under an Article 4 direction, that changes the design before it changes the price.
We do not submit planning applications on your behalf. Where one is needed we will tell you what it is for and which council it goes to, and we will give you the unit's dimensions and position so the form can be filled in accurately.
None of this is legal advice, and a council's own planning team is the only body that can give a binding answer about your specific address. If you want certainty before committing, a lawful development certificate is the formal route.
The ranges this applies to
Every price is fully installed and includes the unit, the installation, the electrical work and VAT.
Instant estimate
Not sure where the outdoor unit would go?
Answer three questions and we will size the room and give you a starting price. Where the position needs a closer look, we say so at the free survey rather than on the day.