Merton: air conditioning planning permission

Since 2025-05-29, England's permitted-development rules let a house fit an air-to-air heat pump - which heats as well as cools - without a planning application in many cases, within set size, siting and noise limits. A cooling-only air conditioning unit does not get that route and needs a full planning application in Merton whatever the property, because on its own it only cools.

Picking a system in Merton therefore decides your planning path as much as your comfort. A unit that heats and cools opens up the permitted-development route on a house; one that only cools never does. About 11% of Merton's EPC-certified stock falls inside a conservation area, concentrated around Kenilworth Avenue, Lambton Road, Dennis Park Crescent; most homes sit outside one, but it is still worth checking the boundary before you commit to a wall-mounted unit.

Flats are the sharpest exception here as everywhere in England: the permitted-development right for an outdoor unit sits with the house, not the flat, so a Merton flat will usually need both freeholder or managing-agent consent and planning permission.

Merton sits in the middle nationally on conservation coverage, at around 11.4% of properties (including parts of Kenilworth Avenue, Lambton Road and Dennis Park Crescent). Whether permitted development is available for your outdoor unit genuinely depends on which part of the borough your home sits in, which is exactly what our checker resolves for your address.

Merton has cooling applications on its record and no decisions on them so far. A rate needs determined cases, so this page gives you none rather than one drawn from applications still in progress.

What actually gets refused, and what councils attach when they approve, is a national picture rather than a local one at the volume of officer reasoning currently published. We set both out with their sample sizes: why cooling applications get refused and the conditions councils attach.

You can also compare what each council decides, where enough decisions exist to publish a figure.

Background noise in Merton sits around 51 dB across the property types we profile during the day, which is the level any outdoor unit has to live inside. A machine that is inaudible on a busy street can be the dominant sound in a still garden, so the local baseline changes the answer.

That makes placement the thing to get right: distance from a neighbour's window, and distance from the boundary, do more for an application than the specification of the unit itself.

None of this is a dealbreaker: councils in Merton approve outdoor units for homes like these all the time. Around 11.4% of local properties sit inside a conservation area, so it is a step to plan for rather than a formality. Being close to a listed building - around 1.2% of homes here sit within 30 metres of one is not the same as your home being listed, and public data can flag conservation status without settling it. This is indicative guidance, not legal advice: confirm the final position with your Local Planning Authority before you install.