Home air conditioning
for houses and flats

A modern 2.5kW unit cooling a bedroom costs roughly 20p to 30p an hour at current rates. In heating mode it is usually cheaper per unit of heat than gas, because the system moves heat rather than burning fuel. We put the figures for your specific rooms in the quote.

For most houses in England, no. The permitted development rules were widened on 29 May 2025 and now cover systems that cool as well as heat. In outline, the outdoor unit can be up to 1.5 cubic metres, detached houses can have two units and everything else one, the old one metre boundary rule has gone, and the installation has to meet the MCS 020 noise standard of 42 dB(A) at the nearest neighbouring habitable room window.

There are limits. It cannot go on a pitched roof, it cannot sit on a wall above ground floor level where that wall faces a highway, and the system must not be for cooling only. Flats are tighter, conservation areas restrict where the unit can sit, and listed buildings and scheduled monuments have no permitted development rights at all.

We check every one of those at survey and tell you before you commit. Where an application is needed, we prepare it. The full rules are set out in our guide to planning permission for air conditioning.

Source: Planning Portal, air source heat pumps, checked September 2026.

One core hole per indoor unit, drilled wet so the dust goes into a bucket rather than your carpet. Everything is sheeted, the pipework is boxed in neatly, and we hoover before we leave.

Yes, and it is an HMRC rule rather than a discount from us. Energy saving materials installed in homes are zero rated from 1 May 2023 until 31 March 2027, and HMRC's position is that most air conditioning units count as air source heat pumps because they heat as well as cool.

The catch is that the same business has to supply and install it. Buy a unit online and pay someone to fit it and the relief is lost. From April 2027 the rate is expected to go back to 5%. Commercial work is charged at the standard rate.

Source: HMRC VAT Notice 708/6, checked September 2026.

It will heat the rooms that have units in them, quickly and cheaply, down to around 5°C outside. Below that it takes longer to reach temperature and on the coldest few days of the year you will probably want your existing heating as well.

It will not give you hot water, and it only warms the rooms where there is an indoor unit. Anyone telling you a couple of wall units will replace a boiler is overselling it.

Indoor units on their lowest fan speed run from about 19 dB(A), which is quieter than a library and well under a fridge. On full boost they reach the high 30s or low 40s, which you notice but can talk over.

Outdoor units sit between the high 40s and low 50s at one metre. That is the figure that matters for neighbours, and the planning noise standard is measured at their window rather than at the unit, so distance, fences and positioning all count in your favour.

On a wall, on the ground on feet, on a flat roof, or on brackets in a lightwell. What it needs is free air: roughly 300mm of clear space behind it and a metre or so in front, nothing boxed in, and somewhere the condensate can drain away.

It also needs to be reachable for servicing, and ideally not directly under a bedroom window, yours or a neighbour's. Long pipe runs from the unit to the rooms are possible but they add cost, so the shortest sensible route usually wins.

As a rough guide, 2.5kW suits a room up to 15m², 3.5kW up to 22m² and 5kW up to 32m². Our size calculator will get you closer using the height, aspect and use of the room.

Those figures move a long way with south facing glass, loft conversions, high ceilings or a kitchen full of appliances. The survey works it out properly rather than rounding up and hoping, which is where oversized, short cycling systems come from.

Usually yes. A single wall unit normally runs on a dedicated circuit from the consumer unit through an isolator next to the outdoor unit. Multi splits and larger systems need a bigger circuit again.

That work is notifiable under Part P of the building regulations. It is arranged as part of the job and the certificate goes in your handover pack, so there is no separate electrician for you to find or pay separately.

Often, but there are two extra hurdles. Your lease usually requires the freeholder's or management company's consent to fix anything to the outside of the building, and the permitted development limits for flats are tighter than for houses.

Where a wall mounted condenser is a non starter, the options are a balcony mounted unit, a shared plant position agreed with the building manager, or a self contained system with no outdoor unit at all. We will tell you at survey which of those applies.