Air Conditioning for Flats: Working Out What's Actually Allowed and What It Costs

Yes — flats can be air conditioned, and a wall-mounted reversible split system is the usual solution. The two things to settle early are practical rather than technical: where the outdoor unit can go and who needs to give permission. Get those clear and the installation itself is often simpler than in a house, because rooms tend to be compact and well insulated by the flats around them.

Permissions come first

A flat needs two separate permissions, and most people underestimate the first one.

Planning permission is usually required. The permitted development right for this equipment in England does extend to a block of flats, but only as one installation for the whole block, capped at 0.6 m³ — against 1.5 m³ and up to two units on a house [1]. It is not a right each leaseholder can exercise for their own flat. In practice, a leaseholder fitting an outdoor unit on a balcony or external wall should expect to need a planning application. Our planning permission guide sets out the full position, including the condition that the unit must not be used solely for cooling.

Freeholder or managing agent consent is separate, and contractual. Planning permission from the council does not give you the right to drill your landlord's wall, and consent under the lease does not substitute for planning. You need both, they are granted by different people on different timescales, and either can refuse. Start both before you get attached to a particular layout.

Outdoor-unit options

The outdoor unit needs airflow, a sensible pipe route and acceptable noise for neighbours — which in a block often live on the other side of a shared wall. A balcony or a section of external wall you have rights to is ideal. Communal walls, walkways and the front elevation are usually off-limits under the lease or the planning rules, so they need checking case by case.

Neighbours usually ask about noise before anything else. A modern condenser typically sits around 45–55 dB(A) measured at one metre, dropping further on night mode, and freeholder consent frequently sets a noise limit or permitted running hours as a written condition, so read those planning and compliance conditions before you choose a position.

When there's no external position

Fully internal air conditioning is its own category, not a split with the outdoor unit hidden. Monobloc and hydronic-style units keep everything inside the flat, rejecting heat through your existing waste pipework or a small discreet vent rather than a wall-mounted condenser, and they can often be built into a false ceiling or similar void instead of taking up living space [1].

If there is genuinely nowhere an outdoor unit can go, a system without an outdoor unit is the honest place to start. Most are monobloc designs: the compressor and condenser sit inside the indoor cabinet, and heat leaves through two neatly cored holes in an external wall instead of a condenser bolted to the brickwork. Because the outside of the building is unchanged, this is usually the fastest route past a freeholder, and some proprietary internal systems are zoned rather than single-room, cooling or heating up to four rooms with independent control [1]. The trade-off is real. Split and multi-split systems remain preferable where efficiency and durability matter, and with the compressor indoors you hear more of the machine. It suits specific situations rather than being a like-for-like replacement, so weigh it up with an installer.

Where an outdoor position does exist, a single split is the standard fit for a living room or bedroom, and a multi-split system serves several rooms from one outdoor unit where the block allows it.

The trade-off is real: no outdoor unit usually means slightly lower efficiency and a higher running cost than an equivalent split, and fewer installers work with these systems regularly. Raise it at survey stage and compare the numbers against typical running costs.

Likely costs

We don't publish fixed prices, because in a flat the access route sets the figure more than the equipment does. The relative bands are predictable, though:

These are relative bands rather than quotes; the estimator returns a tailored figure.

In a flat, price follows access more than equipment. The driver most people miss is getting the outdoor unit into position: no goods lift, or a unit that has to be craned or roped to a high-level bracket, and access equipment plus labour can outweigh the hardware. Routing pipework through a communal riser adds consent and making-good on top.

The biggest single swing on air conditioning installation london cost in flats is access: no goods lift, or pipe routing through communal areas needing management-company sign-off, adds hours at London labour rates.

Getting it scoped

An installer survey confirms what is genuinely feasible — the outdoor position, the pipe route and whether any planning application is likely to be needed alongside your freeholder's consent. Start with our system finder, then request an installer match.

Common questions about air conditioning in flats

Can I get air conditioning in a flat with no outdoor space at all?

Yes. Fully internal monobloc and hydronic systems need no external condenser, so they suit flats with no balcony or usable wall. Expect a higher running cost and a shorter list of experienced installers, which makes a proper survey worthwhile.

Is a portable air conditioner a good alternative?

A portable air conditioner is a stopgap. It vents through a window hose, runs noisier and less efficiently than a fixed unit, and cools one room at a time. Fine for occasional heat, not a replacement for a permanent system in a home.

How long does installation take?

A straightforward single split is usually a day. Multi-split or fully internal work runs to two or three days, and lift restrictions or communal-access permissions can stretch the timeframe further.