Air Conditioning Planning Permission UK: What You Actually Need

If you are installing an air-to-air heat pump on a standard house and the unit is under 1.5 cubic metres, you almost certainly do not need planning permission. That covers the vast majority of domestic units with room to spare. Rules changed in May 2025 and most search results online have not caught up. What matters more than size is function. A unit that cools only, with no heating capability, is treated differently under planning law, whatever its dimensions. This page sets out exactly where you stand, and why that distinction decides everything else.

The key distinction: air-to-air heat pump vs cooling-only AC unit

Most guidance treats air conditioning as one category. It is not, and the difference determines whether you need planning permission at all. Understanding air conditioning planning permission UK law starts here, before volume limits or boundary distances come into it.

Permitted development rights for these units sit under Class G, and Class G was written for air source heat pumps. An air-to-air heat pump provides both heating and cooling from the same outdoor unit, and it qualifies for permitted development subject to the conditions below. A cooling-only unit, sometimes marketed simply as air conditioning with no heating function, does not qualify under Class G at all. Size becomes irrelevant. If the unit cannot heat, you need full planning permission regardless of how small it is.

This is the single biggest correction this page makes to what you will find elsewhere. It also connects to the certification choice covered in our comparison of air con vs air-to-air heat pump systems. Choosing a unit that heats as well as cools is not only a running cost decision. It is a planning decision.

Permitted development for houses: the rules explained

For a house, an air-to-air heat pump installation falls under permitted development, meaning no planning application is needed, provided all of the following are met:

The nine conditions

• The unit must provide a heating function. Cooling-only units are excluded entirely.
• The combined volume of all outdoor parts must not exceed 1.5 cubic metres. This limit was raised from 0.6m³ in May 2025 for houses.
• Only one unit is permitted per property under these rights.
• The unit must not be installed on a pitched roof.
• It must not be installed on a wall or roof that faces a highway.
• It must not be installed in a conservation area, National Park, Area of Outstanding Natural Beauty, or World Heritage Site.
• It must not be installed on a listed building.
• The unit must meet the MCS 020 noise standard. Ask your installer to confirm in writing that the specific model you are quoted meets the current threshold, since the standard has been under review and installers are best placed to confirm the figure that applies at the time you install.
• It must not be installed within one metre of the property boundary.

Permitted development for flats: stricter rules

If you live in a flat, the May 2025 uplift does not apply to you. The volume limit for flats remains 0.6 cubic metres, and the other conditions are tighter:

• Volume limit: 0.6 cubic metres, unchanged since before the 2025 update.
• Maximum one unit per flat.
• Must not be installed on a pitched roof.
• Must not be in a conservation area or on a listed building.
• Must not face a highway above ground floor level.

Planning permission is only one part of the picture for flats. Leasehold consent from your freeholder is a separate requirement, and permitted development rights do not grant you the right to attach equipment to a building you do not own outright. We cover that separately in our guide to installing air conditioning in a flat under leasehold rules, which is worth reading alongside this page if you are in a flat.

When you definitely need planning permission

You will need a full planning application if any of the following apply:

• The unit is cooling-only, with no heating function, regardless of size.
• The unit exceeds the volume limit for your property type.
• Your property is in a conservation area, on a listed building, in a National Park, an Area of Outstanding Natural Beauty, or a World Heritage Site.
• The proposed position faces a highway, or sits on a pitched roof.
• You already have one unit installed and want a second.
• You are in a flat and cannot meet the stricter flat conditions above.

Conservation areas and listed buildings

In a conservation area, Class G permitted development rights do not apply at all, whatever the unit’s size or type. A full planning application is required. Councils vary considerably in how they approach these applications. Some are pragmatic about discreetly positioned units on the rear of a property. Others are restrictive regardless of positioning. A pre-application inquiry, usually free or low-cost through your local planning authority, will tell you the council’s likely position before you commit to a full application.

Listed buildings carry an additional requirement. Listed building consent is a separate process from planning permission, and it applies to any external alteration, not only air conditioning. Grade I and Grade II* buildings face the most restrictive approach of all. If your property is listed, bring in an architect or heritage consultant who has handled listed building consent before, rather than relying on a standard installer quote to navigate this.

What to do if planning permission is required

A householder planning application is the route for most residential cases. The current fee in England is around £258, though this changes periodically, so check the current figure on the planning portal before applying. Processing typically takes around 8 weeks. An installer experienced in planning applications can help prepare the drawings and supporting information a council will expect to see, which usually makes the process considerably smoother than handling it alone.

The most common mistake homeowners make is assuming a small unit automatically clears every hurdle. It does not. Function matters as much as size. If you want to avoid a planning application entirely, choose a unit that heats as well as cools, keep it under 1.5 cubic metres, and check the position against the conditions above before your installer books the work. For most standard houses outside conservation areas, that is a straightforward bar to clear.

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