This is one of the most common things stopping people getting in touch about air conditioning — a vague worry that it’ll involve planning permission, forms, and delay. For most homes, it doesn’t. But “most” isn’t “all,” and it’s worth knowing exactly where the line sits before you commit to anything.

The Short Answer

Indoor units are always exempt from planning permission — they’re inside your home, so planning law simply isn’t concerned with them. The part that matters is the outdoor condenser unit, and for most houses, that’s covered by Permitted Development rights, meaning no planning application is needed at all, provided it meets a specific set of conditions.

The Conditions That Actually Matter

For a typical house, an outdoor condenser unit is Permitted Development if it meets all of the following:

Size — the unit needs to fall under a specific volume threshold. This threshold was increased in rule changes from May 2025, so it’s worth checking the current figure rather than relying on older guidance still floating around online.
Position relative to boundaries — the unit needs to sit a minimum distance back from the property boundary if it’s near the edge of your plot.
Not on a wall or roof facing a highway above ground floor level — a condenser mounted high up on a street-facing wall is treated differently to one tucked round the side or back of the property.
Property type and location — the property must not be a listed building, and must not sit within a conservation area or an Article 4 direction area.

When You Do Need Planning Permission

Planning consent becomes necessary for larger commercial-scale systems, for flats (which generally don’t carry the same permitted development rights as houses), and for any installation on a listed building or within a conservation area or Article 4 zone — regardless of the size of the unit.

Noise Standards Are Part of This Too

Permitted development for AC isn’t purely about size and position — there’s also a noise standard the outdoor unit needs to meet at the nearest neighbour’s window or door, under MCS 020. This standard has become stricter over time, which is one more reason unit selection and positioning benefit from a proper survey rather than guesswork.

If You’re Not Sure Where You Stand

If your property is listed, in a conservation area, or you’re simply not sure, this is exactly the kind of thing worth checking before you buy equipment, not after. Get in touch and we’ll talk through your specific property before recommending anything.

Planning rules carry genuine local authority discretion and property-specific nuance — this is general guidance, not a substitute for checking your specific situation.

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