Types of Air Conditioning Unit in the UK: Which Suits Your Home?
Portable, through-the-wall, wall-mounted, floor-standing, multi-split, cassette and ducted: what each one is like to live with, how it is fitted, and how much mess the fitting makes.
The short answer
- For one room, most homes are best served by a wall-mounted split system: quiet indoors, efficient, heats as well as cools, and usually fitted in a day through one small hole.
- For several rooms, a multi-split runs them all from one outdoor unit. A floor-standing console suits rooms with sloping ceilings or no high wall.
- Ducted systems and ceiling cassettes hide almost everything, but mean cutting ceilings, so they suit renovations, extensions, new builds and commercial spaces.
- We fit wall-mounted split, multi-split, ceiling cassette and ducted systems, and the survey tells you which suits each room.
- Units with no outdoor box, portable or through-the-wall, avoid the outside unit at the cost of noise and efficiency indoors.
At a glance
| Type | Best for | Outdoor unit? | Heats too? | Typical fitting time | Mess when fitted |
|---|---|---|---|---|---|
| Portable | Renters, and a room that needs cooling for a few hot days a year | No: a hose out of a window | A few models | Minutes: no installer | Minimal (1 of 5) |
| Through-the-wall | A single room where an outdoor unit is not allowed or not possible | No: two grilles in the wall | Reversible models | Usually a day | Moderate (3 of 5) |
| Wall-mounted split | Bedrooms, living rooms, home offices, garden rooms and extensions | Yes: one per room | Yes | Usually one day | Low (2 of 5) |
| Floor console | Loft rooms with sloping ceilings, under windows, conservatories, and rooms used mostly for heating | Yes | Yes | Usually one day | Low (2 of 5) |
| Multi-split | Two or more rooms, with space outside for only one unit | Yes: one for several rooms | Yes, one mode at a time | One to three days, depending on the rooms and pipe routes | Moderate (3 of 5) |
| Ceiling cassette | Large open-plan rooms and extensions with a deep enough ceiling void, and offices, shops and restaurants | Yes | Yes | One to two days per unit in a tiled ceiling; longer in plasterboard | Significant (4 of 5) |
| Ducted | Renovations, extensions, loft conversions and new builds, while the ceilings are open | Yes | Yes | Several days, best planned into building work | High (5 of 5) |
A unit that heats is a reversible model, working as an air-to-air heat pump; every system we fit is one. Fitting times are for a typical home with straightforward access. Mess is rated from 1 (nothing to clear up) to 5 (building work), and is explained for each type below.
Portable air conditioners
A self-contained box on wheels that plugs into a socket. Everything, compressor included, sits in the room, and the heat it removes is blown out through a wide hose hung out of a window.
Best for: Renters, and a room that needs cooling for a few hot days a year
Good points
- Nothing to install: wheel it in, fit the window kit and plug it in
- The cheapest to buy, and it moves from room to room or house to house
- Sealed at the factory, so no refrigerant engineer is involved
Drawbacks
- The noisiest option, because the compressor is in the room with you
- A single-hose unit blows air it has already cooled out of the window, and warm air leaks back in under doors and round windows to replace it
- The window stays open around the hose, which lets in draughts and is a security worry
- Takes floor space, and most models only cool
- Not covered by the 0% VAT rate for energy-saving installations
How it's fitted
- Fit the window kit: a fabric or plastic panel that closes the gap around the hose.
- Stand the unit near the window and connect the hose.
- Empty the water tank now and then, unless the model re-evaporates it into the exhaust air.
Typical fitting time: Minutes: no installer
No drilling and no tools. The only trace is the window kit.
Through-the-wall units (no outdoor unit)
A single unit fixed high on the inside of an outside wall, with the compressor built in. It breathes through two large round holes in the wall, covered by grilles outside, so nothing hangs on the outside of the house.
Best for: A single room where an outdoor unit is not allowed or not possible
Good points
- Nothing outside but two round grilles
- No refrigerant pipework on site: the unit comes sealed from the factory
- Reversible versions heat as well as cool
Drawbacks
- Louder in the room than a split system, because the compressor is inside: one popular model is rated 32–43 dB(A) indoors, where the quietest wall-mounted split indoor units run from about 19 dB(A)
- Two large holes, 162 mm or 202 mm across, have to be cored through the wall
- Less powerful than a split (around 3.5 kW at most) and less efficient, so best for one modest room
- Has to go on an outside wall
How it's fitted
- Mark the two hole positions on an outside wall, following the maker’s template.
- Core-drill the two large holes, sloping slightly down to the outside.
- Fit the mounting bracket, hang the unit and connect its condensate drain.
- Fit the grilles on the outside, and connect the power.
Typical fitting time: Usually a day
Coring two holes that size is the loud, dusty part: a careful installer uses wet coring or dust extraction and sheets the room. After that it is little more than hanging a unit.
Wall-mounted split systems
The usual choice for heating and cooling a single room. A slim indoor unit high on the wall is joined by two insulated copper pipes, a drain and a cable to an outdoor unit, which holds the noisy compressor. A reversible model is an air-to-air heat pump, so it heats as well as cools.
Best for: Bedrooms, living rooms, home offices, garden rooms and extensions
Good points
- The quietest indoors, because the compressor lives outside: the quietest indoor units run from about 19 dB(A)
- The most efficient type, and it heats as well as cools
- Only one small hole through the wall
- Installation in a home is zero-rated for VAT until 31 March 2027
Drawbacks
- The indoor unit is on show, and so is the pipe trunking where the pipes cannot be hidden
- The outdoor unit needs a spot on a wall or the ground, and has to meet the planning conditions below
- Needs its own electrical circuit from your consumer unit
How it's fitted
- Agree where both units and the pipe run go.
- Fix the indoor unit’s mounting plate to the wall.
- Drill one hole about 65 mm across (80 mm for larger units) through the outside wall, sloping slightly down to the outside so water cannot run back in.
- Mount the outdoor unit on wall brackets or on feet on the ground.
- Run the copper pipes, drain and cable between the two, in trunking where they cannot be hidden.
- Add a dedicated electrical circuit from the consumer unit.
- Pressure-test the pipework with nitrogen, pull a vacuum, then release the refrigerant and test-run the system in heating and cooling.
Typical fitting time: Usually one day
One small hole, a few fixings and a line of trunking. The dust stays around the hole, and the gap around the pipes is sealed so the wall is left weathertight.
Floor-standing console units
A split system whose indoor unit sits on the floor or low on the wall, about the size of a radiator. It connects to an outdoor unit exactly as a wall-mounted split does.
Best for: Loft rooms with sloping ceilings, under windows, conservatories, and rooms used mostly for heating
Good points
- Fits where there is no high wall to hang a unit on
- Warm air comes out at floor level, so it heats a room much as a radiator does
- Easy to reach for cleaning the filters
Drawbacks
- Takes wall and floor space you might want for furniture
- Draining water away from low down is harder, so it more often needs a small condensate pump
- Fewer models to choose from than wall-mounted units
How it's fitted
- Fix the unit to the floor or low on the wall.
- Drill one hole through the outside wall at low level, or run the pipes under the floor.
- Everything else is as for a wall-mounted split: outdoor unit, pipes, drain, electrics, pressure test, vacuum and test run.
Typical fitting time: Usually one day
The same as a wall-mounted split: one small hole and a short pipe run, sometimes with a floorboard lifted to hide the pipes.
Multi-split systems
One outdoor unit serving several indoor units, each on its own pair of pipes. The indoor units can be any mix of wall-mounted, floor-standing and ducted, and each room has its own control.
Best for: Two or more rooms, with space outside for only one unit
Good points
- One outdoor unit instead of several: two to five rooms is common, and some outdoor units take six
- Each room sets its own temperature
- Usually costs less per room than separate single systems
Drawbacks
- Every room runs in the same mode: one room cannot heat while another cools
- If the outdoor unit fails, every room it serves loses heating and cooling
- Longer pipe runs, often through lofts or floors or in more trunking outside, within the maker’s length limits
- The outdoor unit is larger than a single split’s, and needs sizing for all the rooms together
How it's fitted
- Fit each indoor unit as for a single split, each with its own hole through the wall.
- Run a separate pair of pipes from each room back to the one outdoor unit, through the loft, under floors or in trunking outside.
- Pressure-test and vacuum every circuit, then commission the system room by room.
Typical fitting time: One to three days, depending on the rooms and pipe routes
A small hole in each room, plus the work of routing several pipe runs to one place: lifted floorboards, work in the loft or more trunking outside, depending on the house.
Ceiling cassettes
A square unit that sits flush in the ceiling and blows air out in four directions, with the working parts hidden in the ceiling void above. The compact size fits a standard 600 mm ceiling tile. We fit them in homes and businesses wherever the ceiling void allows.
Best for: Large open-plan rooms and extensions with a deep enough ceiling void, and offices, shops and restaurants
Good points
- Air spreads four ways, so a large room is heated or cooled evenly
- Sits flush in the ceiling, out of reach, with no wall or floor space taken
- A built-in pump lifts the condensate away, so it can go where a gravity drain cannot
Drawbacks
- Needs roughly 300 mm of space above the ceiling, which most UK homes do not have between floors
- A plasterboard ceiling has to be cut and made good
- The ceiling must be about 2.5 m or more above the floor, which rules out many bedrooms
How it's fitted
- Check the ceiling void is deep enough, and find the joists.
- Remove a ceiling tile, or cut a square opening of about 600 mm in plasterboard.
- Hang the unit on threaded rods from the structure above.
- Run the pipes, drain and cable through the void to the outdoor unit, then pressure-test, vacuum and commission.
- Fit the decorative panel; in plasterboard, finish and decorate around it.
Typical fitting time: One to two days per unit in a tiled ceiling; longer in plasterboard
In a tiled office ceiling, a tile comes out and little else. In a plasterboard ceiling, cutting the opening is dusty, and the edges need filling and decorating afterwards. In an extension or renovation, the opening is cut before the ceiling is decorated, so there is little extra mess.
Ducted air conditioning
The indoor unit is hidden in a ceiling void, loft or bulkhead, and ducts carry the air to slim grilles in one or more rooms. Only the grilles are visible.
Best for: Renovations, extensions, loft conversions and new builds, while the ceilings are open
Good points
- Nothing on show but the grilles
- Quiet in the room, because the unit is somewhere else
- One unit can serve several rooms through its ducts
Drawbacks
- The most disruptive to fit into a finished home
- Needs a ceiling void or loft space: slim units want around 240 mm
- Usually needs a condensate pump, and an access panel for servicing and filter cleaning
- Costs more than wall-mounted units for the same rooms
How it's fitted
- Design the duct runs and grille positions with the building work.
- Hang the unit in the void or loft, with an access panel below it.
- Run the ducts to each grille, and cut the grille openings.
- Run the pipes, drain and cable to the outdoor unit, then pressure-test, vacuum and commission.
- Box in and make good any bulkheads, then decorate.
Typical fitting time: Several days, best planned into building work
In a finished home it means opening ceilings, building bulkheads and redecorating: building work, not just an installation. Planned into a renovation, the extra mess is small.
What happens on the day, whichever split system you choose
- A survey first: the installer checks the walls, the route for the pipes, where the outdoor unit can go, the electrics and the drain.
- Dust sheets down, then the indoor unit’s fixings and the hole (or holes) through the outside wall.
- The outdoor unit goes on wall brackets or on feet on the ground, ideally close to the room it serves.
- Insulated copper pipes, a condensate drain and a control cable are run between the units, hidden where possible and in trunking where not.
- A new electrical circuit is run from the consumer unit. That is notifiable work under Part P of the Building Regulations, so it is done and certified by a registered electrician.
- The pipework is pressure-tested with nitrogen to find any leak, then a vacuum pump draws out air and moisture before the refrigerant is released.
- The system is test-run in heating and cooling, you are shown the controls, and the rubbish goes with the installer.
How we keep the mess down
- Dust sheets over floors and furniture, and furniture moved clear of the work.
- Core drilling with dust extraction, or wet coring, so the dust is caught at the hole.
- The hole sloped to the outside and sealed around the pipes, so no draughts or water get in.
- Pipes hidden in walls, lofts or floor voids where the route allows, and in neat trunking where it does not.
- Everything hoovered and the packaging taken away at the end of the day.
Rules worth knowing before you choose
Split systems need an F-gas certified installer
In Great Britain, anyone installing a system that holds refrigerant must hold an F-gas qualification and work for a certified company. That covers every split, multi-split, cassette and ducted system, including pre-charged “quick connect” kits sold online: retailers are not allowed to sell one to a homeowner without evidence that a certified company will fit it. Portable and through-the-wall units come sealed from the factory, so fitting one does not involve refrigerant work.
Planning permission (England)
Since 29 May 2025, an air-to-air heat pump that is not used solely for cooling can be installed under permitted development. The main limits: one outdoor unit on most houses, two on a detached house; the outdoor unit no bigger than 1.5 cubic metres; not on a pitched roof; and it must pass the MCS 020 a) noise check at the nearest neighbour’s window. Listed buildings, and walls or roofs facing a road in a conservation area, need permission, as do cooling-only units. Wales adopted similar rules from 1 June 2026. Scotland and Northern Ireland have their own rules, so check with your council there.
Flats and leasehold homes
Even where planning permission is not needed, an outdoor unit on a block of flats usually needs the freeholder’s or management company’s consent under the lease.
0% VAT on installation
Installing a fixed air source heat pump in a home is zero-rated for VAT until 31 March 2027, and HMRC treats most air conditioning units as air source heat pumps. Portable units do not qualify, and equipment bought without installation is standard-rated.
Which one is right for you?
One room you use most days
Wall-mounted split. Quietest indoors, most efficient, and usually fitted in a day.
A loft room, a sloping ceiling or no high wall
Floor console. Fitted like a wall-mounted split, just lower down.
Several rooms, and room outside for one unit
Multi-split. One outdoor unit, a control in every room.
Renovating, and you want nothing on show
Ducted. Only grilles are visible, and the ceilings are open anyway.
A large open-plan room, an extension or an office with a deep ceiling void
Ceiling cassette. Even airflow from a unit flush with the ceiling.
No outdoor unit allowed
Through-the-wall unit. Two grilles outside, at the cost of noise indoors.
Renting, or cooling for a few days a year
Portable. No installation, but noisy and much less effective.
Video transcript
Air conditioning comes in a few different shapes. Here’s what each one is like to live with, and how much mess it makes to fit.
A portable unit just plugs in. Nothing to fit. But its hose hangs out of an open window, and it’s noisy, and much less effective.
A through-the-wall unit has no outdoor box. Instead, two big holes are cored right through the wall. That’s the dusty part. And the compressor hums away inside the room.
The wall-mounted split is the usual choice for one room. The noisy part sits outside. One small hole takes the pipes through, and it’s usually fitted in a day, with very little mess.
A floor console goes in the same way, just lower down: handy under a window, or beneath a sloping ceiling.
A multi-split runs several rooms from one outdoor unit. There’s a hole and a pipe run for each room, so it takes a little longer.
A ceiling cassette sits flush in the ceiling and spreads air four ways. But it needs a deep ceiling void, and a square opening cut to fit it.
Ducted air conditioning hides in the loft or ceiling, with only slim grilles on show. It’s the neatest to live with, and the most work to fit, so it’s best planned with a renovation.
Every split system needs an F-gas certified engineer. And the systems we fit heat as well as cool. They’re air-to-air heat pumps.
Arctic Air Conditioning. We’ll help you pick the right one.
Frequently asked questions
Which type of air conditioning is best for a UK home?
For one room, a wall-mounted split system: it is the quietest indoors, the most efficient, heats as well as cools, and usually goes in within a day through one small hole. For several rooms, a multi-split runs them all from one outdoor unit. Ducted systems suit renovations where the ceilings are open anyway, and a portable unit only makes sense for occasional use or where you cannot fix anything to the building.
How big is the hole for an air conditioning unit?
For a wall-mounted or floor-standing split system, usually one hole about 65 mm across, or 80 mm for larger units, sloping slightly down to the outside. A through-the-wall unit with no outdoor unit needs two much larger holes, 162 mm or 202 mm across.
How long does it take to install air conditioning?
A single wall-mounted split with a short pipe run is usually fitted in a day. A multi-split takes one to three days depending on the number of rooms and how the pipes are routed. Ducted systems take several days and are best planned into building work.
Is installing air conditioning messy?
For a wall-mounted split, not very: one small hole, a few fixings and some trunking, with the dust kept to the area around the hole. Through-the-wall units need two large holes, which is dustier. Ceiling cassettes and ducted systems mean cutting ceilings and redecorating, unless they go in during a renovation.
Can I have air conditioning without an outdoor unit?
Yes, with a portable unit, which vents through a hose out of a window, or a through-the-wall unit, which breathes through two grilles in the wall. Both keep the compressor inside, so both are louder in the room and less efficient than a split system.
Can you fit a ceiling cassette in a house?
Yes, where there is room for one. A cassette needs roughly 300 mm of space above the ceiling and a ceiling about 2.5 m or more high, so it suits large open-plan rooms and extensions better than most bedrooms. We fit them, and the survey checks the depth of the void, which way the joists run and where the condensate can drain.
Do I need planning permission for air conditioning?
In England, usually not for a unit that heats as well as cools. Since 29 May 2025, an air-to-air heat pump that is not used solely for cooling can be permitted development, within limits: one outdoor unit on most houses (two on a detached house), no bigger than 1.5 cubic metres, and meeting the MCS 020 a) noise standard at the nearest neighbour’s window. Cooling-only units, listed buildings, and walls facing a road in a conservation area need permission. Wales has similar rules; Scotland and Northern Ireland differ, so check with your council.
Can I fit a split air conditioning system myself?
No. In Great Britain a split system must be installed by an F-gas qualified engineer working for a certified company, and that includes pre-charged “quick connect” kits: retailers are not allowed to sell one to a homeowner without evidence that a certified company will install it.
Not sure which type suits your rooms?
Two minutes with our estimator gets you a realistic range. A free survey looks at your walls, ceilings and outside space and turns it into a fixed quote, with no obligation and no hard sell.
Sources
- GOV.UK: Qualifications required to work on equipment containing F gas
- GOV.UK: Certification for companies working on equipment containing F gas
- Regulation (EU) 517/2014 as retained in Great Britain, Article 11 (sale of pre-charged equipment)
- The Town and Country Planning (General Permitted Development etc.) (England) (Amendment) Order 2025
- Planning Portal: Air source heat pumps
- MCS 020 a): permitted development noise standard for air source heat pumps
- Welsh Government: Planning permission for heat pumps
- HMRC: VAT on energy-saving materials and heating equipment (Notice 708/6)
- Daikin: FTXM wall-mounted unit installation manual (hole size, drain)
- Daikin: Perfera wall-mounted unit product profile (sound levels)
- Daikin: Why multi-split indoor units cannot heat and cool at the same time
- Daikin: FFA ceiling cassette installation manual (ceiling void and opening)
- Daikin: FDXM slim concealed ducted unit
- Olimpia Splendid: Unico Pro through-the-wall unit data (wall holes, sound)
- US Department of Energy: Portable air conditioner test procedure (single-hose infiltration)
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