The quick answer: most UK homes use a split system
If you are searching for air conditioning units for your home, the short answer is that most UK houses end up with a split system. That means a slim indoor unit mounted on the wall, connected to an outdoor unit by pipework through a small hole, rather than one large machine sitting in the room.
The right type depends on how many rooms you want to cool, where an outdoor unit could go, and whether you want the system to heat as well. One room usually means a single split. Several rooms usually means a multi-split or more than one system. Portable units are the main option where a fixed installation is not possible.
This guide explains each type in plain English, what it typically costs to install, and how to work out which one suits your house before you speak to an installer.
What a split air conditioner actually is
A split air conditioner is called a split because the system is divided into two halves. The indoor unit holds the fan and heat exchanger that condition the room. The outdoor unit holds the compressor, which does the noisy work outside, which is why fixed systems are usually much quieter indoors than portable units.
The two halves are connected by insulated refrigerant pipework, a cable and a small condensate drain, normally routed through a modest hole in an external wall. Refrigerant carries heat between the units: out of the room in summer, and into the room in winter when the system runs in heating mode.
Nearly all modern split systems are reversible air-to-air heat pumps. That matters for comfort and for value, because the same installation can provide efficient heating for the rooms it serves as well as summer cooling.
- Indoor unit: usually mounted high on the wall, with a washable filter and remote or app control.
- Outdoor unit: houses the compressor and fan, sited on an external wall, on the ground or on a flat roof.
- Pipework: insulated copper pipes carrying refrigerant between the two units.
- Condensate drain: removes the moisture the indoor unit pulls out of the air while cooling.
The main types of unit compared
Most homeowner decisions come down to four options. The names sound technical, but the differences are simple: how many rooms are covered, whether the unit is fixed or portable, and how visible the equipment is.
The installed price ranges below match our installation cost guide and are indicative for 2026. The final quote depends on your property, pipe routes, access and electrical work, so treat these as budgeting ranges rather than fixed prices.
Single split system
around £1,500 to £3,500 installed
One indoor unit and one outdoor unit serving one room. The default choice for a bedroom, living room, home office or garden room.
Multi-split system
around £3,000 to £7,500 installed
One outdoor unit running indoor units in two or three rooms. Useful where outside space, planning considerations or neighbour impact limit the number of outdoor units.
Ducted or whole-home system
£7,500 to £15,000+ installed
A concealed unit in the loft or ceiling void supplying air through discreet grilles. Suits larger budgets, renovations and homes where visible wall units are not wanted.
Portable unit
often £250 to £700 to buy
A plug-in unit with an exhaust hose through a window. No installation needed, but noisier and less efficient, so best treated as a short-term or rental option.
Indoor unit styles within a fixed system
Within a fixed system, you can also choose the style of indoor unit. Wall-mounted units are by far the most common in UK homes and usually the best value, which is why most quotes start there.
Floor-mounted units sit low on the wall like a slim radiator, and can suit rooms with sloped ceilings, low walls under windows or loft conversions. Ceiling and ducted options hide most of the equipment, but they need space above the ceiling and more installation work, so they cost more.
- Wall-mounted: the standard high-wall unit, widely available and usually the most affordable to install.
- Floor-mounted: a radiator-height unit for lofts, dormer rooms and spaces with limited high wall space.
- Ceiling cassette: sits flush in the ceiling, more common in larger rooms, extensions and offices.
- Ducted: fully concealed with only grilles visible, at a higher installation cost.
Fixed split system or portable unit?
If you are weighing a portable unit against a fixed installation, the honest answer is that they solve different problems. A portable unit is a quick, temporary fix for a hot spell. A fixed split system is a longer-term comfort upgrade for the room.
Portable units have to push warm air out through a hose, usually through a window, and all of the machinery sits in the room with you. That makes them noisier and generally less efficient than a fixed system doing the same job. For regular use in a bedroom or living room, a fixed unit usually gives better comfort for the money over time. Our running costs guide compares the two in more detail.
Fixed split system
- Quieter indoors because the compressor sits outside.
- More efficient for regular use, and most can heat as well as cool.
- A neat, permanent installation with proper controls and timers.
- Needs professional installation and a suitable outdoor unit position.
Portable unit
- No installation needed and it can move between rooms.
- Warm air must exhaust through a hose, so a poor window seal lets heat straight back in.
- All of the machinery is in the room, so it is noticeably noisier.
- Best for renters, occasional use or as a stopgap while planning a fixed system.
Which type suits your house?
The easiest way to choose is to start with the rooms rather than the products. Decide where heat actually causes a problem in your house, then match the system to those rooms and to where an outdoor unit could realistically sit.
Be realistic about future use as well. Many homeowners start with one bedroom and later wish they had planned for the living room too. If several rooms are likely within a few years, ask installers to quote a multi-split, or at least to position the first outdoor unit with expansion in mind.
- One hot bedroom or home office: a single split is usually the simplest and cheapest fixed option.
- Two or three rooms: compare a multi-split against separate single splits, because pricing and practicality vary by property.
- Whole house or major renovation: consider a ducted design or a combination of systems planned around the property.
- Flat, rental or nowhere suitable for an outdoor unit: a portable unit may be the practical fallback, but check the building rules and any freeholder consent first.
- No external wall in the room: longer pipe runs are often possible, but they add cost and need a properly surveyed route.
Sizing, heating and efficiency basics
Whichever type you choose, the unit needs to be sized for the room. Capacity is usually quoted in kW or BTU, and a bigger number is not automatically better. An oversized unit can feel draughty and noisy, while an undersized one runs hard and still struggles on the hottest days.
Check the heating side too. Because most fixed units are reversible air-to-air heat pumps, the same system can provide efficient heating in spring, autumn and milder winter weather. Efficiency labels help when comparing models: SEER describes seasonal cooling efficiency and SCOP describes seasonal heating efficiency, and higher is better in both cases.
Our BTU guide and running costs guide cover sizing and electricity use in more detail if you want to go deeper before requesting quotes.
What to ask when comparing quotes
Once you know roughly which type of unit suits your home, quotes become much easier to compare, because you can check that each installer is pricing the same kind of system rather than simply picking the cheapest headline number.
A good installer should explain why they are recommending a single split, multi-split or ducted design for your rooms, where the outdoor unit will go and how the system has been sized. If two quotes propose different types of system for the same rooms, ask each installer to explain their reasoning.
AC Journey does not install systems directly. We help homeowners compare quotes from vetted UK installers, so you can weigh system type, sizing, cost and aftercare together before deciding who to work with.
- Which type of system is being proposed, and why does it suit these rooms?
- Where will the outdoor unit sit, and has noise for neighbours been considered?
- Is the system reversible, and what heating performance can we expect?
- What capacity is proposed for each room, and how was it sized?
- Could the system be extended later if we add more rooms?
- What is included: pipework, electrics, commissioning, warranty and VAT treatment?
Common questions
What type of air conditioning unit is best for a home in the UK?
For most UK homes, a fixed split system is the best starting point: a wall-mounted indoor unit connected to an outdoor unit. One room usually suits a single split, several rooms may suit a multi-split, and portable units are mainly a fallback where a fixed installation is not possible.
What is a split air conditioner?
A split air conditioner is a system divided into two halves: an indoor unit that conditions the room and an outdoor unit that houses the compressor. They are connected by insulated refrigerant pipework through a small hole in an external wall, which keeps the noisy components outside.
Can one outdoor unit cool more than one room?
Yes. A multi-split system connects one outdoor unit to several indoor units, often two to five depending on the model. Each room keeps its own indoor unit and control, which is useful where outside space for multiple outdoor units is limited.
Do home air conditioning units heat as well as cool?
Most modern fixed units do. They are reversible air-to-air heat pumps, so the same system can cool in summer and provide efficient heating in cooler months. Check the SCOP rating and ask the installer what heating performance to expect in your rooms.
How much does a home air conditioning unit cost?
As a 2026 guide, a single-room split system often costs around £1,500 to £3,500 installed, a two to three room multi-split around £3,000 to £7,500, and ducted or whole-home systems £7,500 to £15,000 or more. Portable units often cost £250 to £700 to buy. The final price depends on your property, so treat these as budgeting ranges.
Are portable air conditioning units worth it?
They can be, for renters, occasional hot spells or rooms where a fixed installation is not possible. For regular use they are usually noisier and less efficient than a fixed split system, so if you expect to cool a room every summer it is worth pricing a fixed installation before buying one.