A fitted single split costs £1,500 to £3,500 across the three mainstream UK cost guides I checked, and the band all three of them cover is £2,000 to £2,500. Each extra room adds £600 to £1,200 when it is done in the same job. Before any of that matters, there is a condition in England the cost guides skip: an outdoor unit that only cools is not permitted development, so it needs planning permission.
There is no official UK statistic for air conditioning installation costs. What exists is commercial cost guides, so that is what these figures are: four published guides, each checked at source on 13 August 2026, shown separately rather than blended into one average that would look more solid than it is.
Sources: OVO Energy, Air Conditioning Installation Cost UK 2026, posted 16 June 2026; Selectra UK, Air Conditioning Units UK 2026, updated 12 August 2026; Heatable, How much does air conditioning cost to install?, updated 10 July 2026; MyJobQuote, Air Conditioning Installation Cost Guide, updated 15 July 2026. Read together, those three guides all cover £2,000 to £2,500, and their outer edges give the wider £1,500 to £3,500. MyJobQuote starts well below all three, so it sets neither band; its own row shows what it does say. None of the four guides states whether its figures include VAT, so read them as headline numbers and ask any quote to set the VAT out separately.
Quotes outside these bands are not automatically wrong, but they are worth asking about. If yours sit a long way apart, the quote check and the reasons quotes differ cover what usually explains the gap.
Published multi-split ranges look wildly inconsistent, and there is a simple reason: the guides mean a different number of rooms. Read as one range they are useless. Read per room they line up.
Sources: OVO Energy, Air Conditioning Installation Cost UK 2026, posted 16 June 2026; Selectra UK, Air Conditioning Units UK 2026, updated 12 August 2026; Heatable, How much does air conditioning cost to install?, updated 10 July 2026.
The number that actually travels between quotes is the uplift for each extra room:
Sources: Heatable, How much does air conditioning cost to install?, updated 10 July 2026; MyJobQuote, Air Conditioning Installation Cost Guide, updated 15 July 2026.
So the useful question for an installer is not what a multi-split costs, but what the first room costs and what each room after it adds. That also makes two quotes for different room counts comparable, which is otherwise close to impossible.
Sources: OVO Energy, Air Conditioning Installation Cost UK 2026, posted 16 June 2026; Heatable, How much does air conditioning cost to install?, updated 10 July 2026; Selectra UK, Air Conditioning Units UK 2026, updated 12 August 2026.
Sources: Heatable, How much does air conditioning cost to install?, updated 10 July 2026; MyJobQuote, Air Conditioning Installation Cost Guide, updated 15 July 2026.
Electrical work is the line that most often turns a tidy quote into a bigger one. If the board cannot take the extra circuit, that is a job of its own with its own certificate; the consumer unit replacement cost page covers what that involves.
Air conditioning is not one of the project types in the cost calculator, so it will not price the unit for you. What it will do is price the renovation this usually sits inside, an extension or a loft conversion, so you can see the air conditioning as one line beside that budget rather than as a number floating on its own.
A published running cost figure usually hides the two things that decide it: the power draw it assumes, and the electricity rate it is priced on. So here both are put in the open instead. The Ofgem price cap for 1 July to 30 September 2026 puts electricity at 26.11p per kWh on a direct debit tariff, about 6% above the 24.67p that applied from 1 April to 30 June 2026. The guides do not agree on which rate to price it at, and not one of them prices on this rate alone, so a pence-per-hour figure copied from any of them sits on some other number. Heatable still calculates on that older 24.67p, so the pence-per-hour figures published there run low.
The sum is power in kW multiplied by hours multiplied by 26.11p. The power figures below are what the guides themselves assume, or are worked back out of their own pence-per-hour figures, and they are printed so you can redo the sum with the draw of the unit you are actually being quoted. These are electrical input figures, not cooling output, which is a much larger number for the same machine.
Sources: Ofgem, Energy price cap unit rates and standing charges, checked 13 August 2026; Selectra UK, Air Conditioning Units UK 2026, updated 12 August 2026; Heatable, How much does air conditioning cost to install?, updated 10 July 2026. Monthly figures assume 6 hours a day for 30 days, rounded to the nearest pound. The arithmetic is mine, on the Ofgem rate above; the power assumptions are the guides.
This is the part that decides whether you can simply book the job. In planning terms the outdoor unit is an air source heat pump, and the Planning Portal sets out the conditions it has to meet to count as permitted development in England. The first one is the one no cost guide mentions.
The condition is listed in six words: "Not used solely for cooling purposes". A cooling-only unit falls outside these rights and needs a planning application. A reversible unit that heats as well as cools can fall inside them, if the rest of the conditions are met.
Worth settling before you order, because it is a property of the equipment rather than of how you use it. Ask the installer to confirm in the quote that the unit provides heating as well as cooling.
Source: Planning Portal, Planning permission: Air source heat pump (England), checked 13 August 2026.
The full set of conditions for the outdoor unit:
It must do more than cool
"Not used solely for cooling purposes"
This is the condition the cost guides skip. A unit that only cools falls outside these rights, so it needs a planning application. A reversible air-to-air unit that heats as well as cools can sit inside them. Which one you are buying is a question for the quote, not for after the install.
Size of the outdoor unit
The outdoor compressor unit, housing included, must not exceed 1.5 cubic metres on a house, or 0.6 cubic metres on a block of flats. Ask for the cased dimensions in the quote, because that is what the volume is measured on.
How many units
"Only the first installation of an air source heat pump would be permitted development, on a house which is not detached or a block of flats. For detached houses, the first two air source heat pumps are considered permitted development."
A multi-split usually runs several indoor units off one outdoor box, so the room count on the inside does not by itself decide this.
Roofs
"Installations on pitched roofs are not permitted development. If installed on a flat roof all parts of the air source heat pump must be at least one metre from the external edge of that roof"
A pitched roof mounting therefore needs an application, whatever the installer would prefer.
Walls facing a road
"must not be installed on any part of a wall above the level of the ground floor storey if that wall fronts a highway"
That is the rule outside a conservation area or World Heritage Site. Inside one it is stricter: the unit must not be installed on a wall or roof which fronts a highway, or be nearer to any highway which bounds the property than any part of the building.
Listed buildings and scheduled monuments
"Permitted development rights do not apply for installations within the curtilage of a Listed Building or within a site designated as a Scheduled Monument"
Listed building consent is a separate requirement of its own, on top of any planning application the work needs.
Certification
"Development is permitted only if the air source heat pump installation complies with the Microgeneration Certification Scheme Planning Standards (MCS 020a)"
The Planning Portal adds that from 28 May 2026, MCS 020a will be the only permitted certification scheme. So this is a condition your installer has to meet, and it is fair to ask how they meet it before you book.
No existing wind turbine
"Development is permitted only if there is no existing wind turbine on a building or within the curtilage of that property."
Rare, but it is an absolute condition rather than a consideration.
Siting and amenity
"Sited, so far as is practicable, to minimise its effect on the external appearance of the building and its effect on the amenity of the area."
This is the condition a neighbour complaint tends to land on, and it is a judgement rather than a measurement.
Removal
"Removed as soon as reasonably practicable when it is no longer needed for microgeneration"
A dead unit left on the wall is not covered by these rights.
Source: Planning Portal, Planning permission: Air source heat pump (England), checked 13 August 2026.
Meeting every one of these conditions is what keeps the work inside permitted development. Miss one and you are into an application, which is a cost and a timetable of its own: see what a planning application costs. The wider rights for extensions and outbuildings sit in the permitted development rules, and the free planning permission check walks your own project through them. Your local planning authority decides in the end, so treat this page as what to ask them, not as their answer.
Because the outdoor unit is treated as a heat pump, these are the same rights people meet when they change how the house is heated. If that is the wider question you are on, heat pump versus boiler covers that comparison.
Worth flagging, because you may land on either one. The Planning Portal FAQ says: "If your home is in a protected area such as a Conservation Area then permission will be required. If you live in a listed building then consent will be required."
The detailed guidance says something narrower: in a conservation area or World Heritage Site the installation can still be permitted development, as long as the unit is not on a wall or roof fronting a highway and not nearer to a bounding highway than any part of the building.
This page follows the detailed guidance, because it tracks the wording of the legislation. The practical advice is the same either way: in a conservation area, a World Heritage Site or a listed building, ask your local planning authority before you order anything.
Sources: Planning Portal, Planning permission: Air source heat pump (England), checked 13 August 2026; Planning Portal Interactive House, Do I need planning permission to add air conditioning to my home?, checked 13 August 2026.
Planning permission and building regulations are two different approvals, and clearing one says nothing about the other. The Planning Portal puts the starting point this way: "Adding air conditioning to your home may be considered permitted development provided all the limits and conditions set out in legislation are met." And on the second track: "The installation of air conditioning must comply with building regulations."
On who should do the work: "It is advisable to contact an installer who can provide the necessary advice, preferably one who belongs to either the Microgeneration Certification Scheme or the relevant Competent Person Scheme."
Source: Planning Portal Interactive House, Do I need planning permission to add air conditioning to my home?, checked 13 August 2026.
How the two approvals divide up is explained in planning permission versus building regulations.
The permitted development conditions on this page are the England rules, from the Planning Portal. Scotland, Wales and Northern Ireland run their own planning regimes, which I have not checked here, so do not read these conditions across to them. The cost figures are UK-wide guide prices.
Two things you will see repeated elsewhere are missing here, because I could not confirm them at source. Leaving them out is rather the point of the page:
I sell no leads and take no commission from installers, so the ranges here follow the sources rather than a booking. The planning conditions come from the Planning Portal and the electricity rate from Ofgem. The prices are estimates published by commercial cost guides, not measured market data and not tariffs, which is exactly why they are shown one by one with the name of the guide attached. Take this into a conversation with a certified installer and your local planning authority rather than instead of one.
In England it turns on one thing most cost guides never mention. The outdoor unit is treated as an air source heat pump, and the Planning Portal lists as a condition that it is "Not used solely for cooling purposes". A cooling-only unit therefore falls outside permitted development and needs a planning application. A reversible unit that heats as well as cools can sit inside those rights, provided the other conditions on size, siting and certification are met too. Scotland, Wales and Northern Ireland run their own planning regimes.
Three of the four UK cost guides checked put a fitted single split at £1,500 to £3,500; the fourth starts far lower, at £550 to £2,100, with an average spend of £1,200. Multi-split systems are quoted anywhere from £2,800 to £10,000, because the guides mean a different number of rooms. The figure that actually travels between quotes is the uplift per extra room, which two guides put at £600 to £1,200 and £800 to £1,200.
At the Ofgem price cap of 26.11p per kWh for 1 July to 30 September 2026, a split system drawing 0.75 kW costs about 19.6p an hour, and a 1.2 kW portable unit about 31.3p. Any published pence-per-hour figure depends entirely on the power draw assumed, so it means nothing without it. It depends on the rate as well, and the guides do not agree on one: the previous cap of 24.67p ran from 1 April to 30 June 2026, about 6% below the rate now in force. Heatable still calculates on that older 24.67p, so the pence-per-hour figures published there run low. That is why the figures here are worked out on the current cap rather than copied across.
On the published figures, doing the rooms in one job is where the saving sits. Two guides price each additional room at £600 to £1,200 and each additional indoor unit at £800 to £1,200, against £1,500 to £3,500 for a standalone single split. Coming back a year later for the second room is a fresh visit with its own set-up costs, so it is worth pricing both orders of doing it before you commit.
The Planning Portal page for England sets no minimum distance from a boundary for a ground-mounted unit, despite what you will read elsewhere. The only distance it gives is that on a flat roof, all parts of the unit must be at least one metre from the external edge of that roof, and installations on pitched roofs are not permitted development at all. Placement is instead governed by the certification standard and by the condition that the unit is sited to minimise its effect on the appearance of the building and on the amenity of the area.
For permitted development in England, yes. The Planning Portal states that development is permitted only if the installation complies with the Microgeneration Certification Scheme Planning Standards (MCS 020a), and that from 28 May 2026 MCS 020a will be the only permitted certification scheme. Separately, the installation has to comply with building regulations, and the Planning Portal advises using an installer belonging to the Microgeneration Certification Scheme or the relevant Competent Person Scheme. Ask how both are covered before you book.