When you want air conditioning in two or more rooms, there are two ways to do it: a separate single-split system for each room, or one multi-split system that serves several rooms. Both are split systems, and both cool and heat. This guide explains the difference and helps you choose.
What is a split system air conditioner?
A split system has two parts: a slim indoor unit on the wall (or in the ceiling) and an outdoor unit outside. They are connected by two small copper refrigerant pipes, a cable and a drain. Because the noisy compressor sits outside, split systems are much quieter and more efficient than portable air conditioners. They are also heat pumps, so the same system heats your home in winter.
What is a single split system?
One indoor unit connected to its own outdoor unit. For two rooms you have two outdoor units, for three rooms three, and so on. Each room is completely independent.
- Each room keeps working if another system fails
- Each room can heat or cool, whatever the other rooms are doing
- Every outdoor unit is sized exactly for its room, which keeps it efficient
- Simpler and usually cheaper to service and repair
- Easy to add another room later: it simply gets its own system
What is a multi split system?
Two to five indoor units connected to one shared outdoor unit. It saves wall space outside, which can matter in terraced houses, flats and properties with strict rules about outdoor units.
- Only one outdoor unit on the wall
- Useful when outside space is limited or rules allow only one unit
- Neat when all the rooms are close to one outside wall
Single split vs multi split at a glance
| Separate single splits | One multi-split | |
|---|---|---|
| Outdoor units | One per room | One for up to five rooms |
| If an outdoor unit fails | Only that room stops | Every room stops |
| Heating and cooling | Each room chooses its own mode | All rooms run in the same mode |
| Guide price, 3 rooms | from £3,590 | from £3,650 |
| Efficiency | Each unit sized to its room | Can be less efficient when only one room runs |
| Servicing and repairs | Simpler | More involved |
| Space outside | More wall space needed | Less wall space needed |
Which is cheaper?
For two or three rooms, separate single splits usually cost about the same as a multi-split, or slightly less. See our guide to how much air conditioning costs for prices by number of rooms. Running costs are often lower with single splits too, because each outdoor unit only works as hard as its own room needs.
Choose separate single splits if…
- You want each room to keep working if one system fails
- You have space on the outside walls for more than one outdoor unit
- Different people want to heat and cool different rooms at the same time
- You want simpler, cheaper servicing and repairs
- You might add more rooms later
Choose a multi-split if…
- Outside wall space is very limited
- Planning, lease or building rules allow only one outdoor unit
- All the rooms are near the same outside wall, so the pipe runs are short
What about ducted air conditioning?
A ducted system hides the indoor unit in the ceiling or loft and sends air to several rooms through slim grilles. It suits new builds, loft conversions and major renovations, and costs more to install. See our air conditioning installation page for all the system types we fit.
Our recommendation
For most homes we recommend separate single-split systems: they are more reliable, often cheaper to run and simpler to look after. We suggest a multi-split when outside space or building rules leave no other option. Either way, we confirm the right choice at the free survey.
Split systems: common questions
Can I add another room later?
With single splits, yes: the new room simply gets its own system. With a multi-split, only if the outdoor unit has a spare connection and enough capacity, so it is worth planning ahead.
How many indoor units can one outdoor unit run?
Most home multi-split systems take two to five indoor units, depending on the model and the size of the rooms.
Are split systems noisy?
Modern indoor units run at around 19 to 25 dB on low, quieter than a whisper. We position outdoor units to keep noise away from bedrooms and neighbours.
Do split systems heat as well as cool?
Yes. They are air-to-air heat pumps, so the same system keeps you cool in summer and heats efficiently in winter.
Not sure which suits your home? Send us a few photos and we’ll recommend the best option, or see a guide price for home air conditioning installation.