The good news is that most homeowners never need to go anywhere near their local council. But the rules changed in 2025, and there are a few situations, particularly common across London, where planning permission for air conditioning genuinely is required. Here’s what actually matters.

Indoor units are never the issue

Whatever system you choose, the wall-mounted unit inside your living room or bedroom doesn’t trigger planning permission of any kind. It’s the bit outside your home, the condenser, that the rules are concerned with. So if you’re only thinking about the visible box on your wall indoors, you can stop worrying and focus on where the outdoor unit is going to sit.

The rule that catches people out: cooling-only vs heating-capable

This is the part most people don’t realise, and it’s the single biggest change to the rules in recent years. Permitted development rights for these external units (under what’s known as Class G of the General Permitted Development Order) only apply if the unit can provide heating, not just cooling. A pure air conditioning unit that only cools will not qualify, and would need a full planning application. A reversible system, often sold as an air-to-air heat pump but doing exactly the same job as air con plus heating, generally will.

In practice, this means the type of system you choose has a direct bearing on whether you need to apply to your council at all. It’s one of the reasons it’s worth having a proper conversation with your installer before you commit to a unit, rather than after it’s already on order.

What “permitted development” actually requires

Assuming your system qualifies, the outdoor unit still has to meet a set of conditions to avoid a planning application:

• It needs to meet recognised noise standards (MCS 020, which has become the standard certification route for these installations).
• On a house, the unit can be up to 1.5 cubic metres, with up to two units allowed on a detached house or bungalow, and one on a semi-detached or terraced property. Blocks of flats have a smaller volume limit.
• It can’t go on a pitched roof, and if it’s mounted on a flat roof, it needs to sit at least a metre back from the edge.
• It should be positioned to keep its impact on how the building looks, and on neighbours, to a minimum.

Meet those and you don’t need to apply for anything. Miss one and the exemption falls away.

Flats, leasehold properties, and shared buildings

If you live in a flat, don’t assume the same freedoms apply. Permitted development rights for these units still exist for blocks of flats, but the volume allowance is lower, and there’s an added layer that has nothing to do with planning at all: your lease. Freeholders and management companies can, and often do, require their own consent before anything goes on an external wall or balcony, regardless of what the council says. It’s worth checking your lease before your heart is set on a particular installer or unit.

Listed buildings and conservation areas

This is where a lot of our enquiries from north and central London come from. Areas like Hampstead, Highgate, Kensington and parts of Marylebone include a fair number of listed buildings and conservation areas, and the rules are stricter there by design. If your property is listed, you’ll typically need listed building consent on top of any planning permission, and councils tend to take a firm line on anything visible from the street. An Article 4 direction, which some conservation areas have in place, can remove permitted development rights entirely, meaning even a fully compliant system would need an application. If you’re not sure whether your street is affected, your local planning department can tell you in a phone call.

Commercial properties

For businesses, it’s safest to assume planning permission will be needed. Commercial systems are usually larger, often involve more than one external unit, and don’t get the same permitted development allowances as a family home. We’ve worked on plenty of commercial installations across London, from offices to restaurant kitchens, and the pattern is consistent: get the planning conversation started early, because it tends to take longer than the installation itself.

Our advice

Planning rules aren’t there to make your life difficult, they’re there so a condenser unit doesn’t end up too close to a neighbour’s window or bolted onto the front of a listed Georgian townhouse. In the vast majority of straightforward residential installations across London, Essex, Hertfordshire and Kent, a well-placed, appropriately sized unit will fall under permitted development and you won’t need to apply for anything.

Where it gets more complicated, listed buildings, conservation areas, flats, or commercial premises, it genuinely pays to have that conversation before the unit arrives rather than after. A good installer should be able to tell you within a few minutes of looking at your property and postcode whether you’re likely to need permission, and can help position the unit to keep you within the rules where possible.

If you’re weighing up a new system and want a straight answer on where you stand, get in touch with our team or give us a call on 020 8989 8989. With 25 years installing air conditioning across London, it’s a question we’re asked most weeks, and one we’re always happy to talk through before you commit to anything.

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