Single split or multi-split air conditioning?
One outdoor unit for each room, or one for several rooms.
The short answer
A single split suits one room, and multi-split air conditioning suits two or more rooms that can share one outdoor unit. If the rooms are far apart, or one must keep running whatever happens, separate single splits may suit better.
How single and multi-split systems differ
Single and multi-split systems work the same way, and the difference is how many indoor units share an outdoor unit. Side by side, they compare like this:
| Point | Single split | Multi-split |
|---|---|---|
| Outdoor units | One for each indoor unit | One for several indoor units |
| Indoor units on one outdoor unit | One | Usually up to five, and six on Mitsubishi Electric |
| Space outside | A box for each room | One larger box |
| Pipes | One run | A separate run from each room |
| Heating or cooling | Each system chooses its own | All rooms share one mode |
| If the outdoor unit fails | One room goes without | Every room goes without |
| Adding a room later | A new system | Possible on some makes, within the outdoor unit’s limits |
The shared mode catches people out, because one room can’t cool while another heats. On a Daikin multi-split, the first room switched on takes priority, and a room set differently waits on standby. Each room still has its own controls.
Sources: the government’s air-to-air review, Daikin UK’s product page and operation manual, and the UK sites of Mitsubishi Electric, Hitachi, LG and Samsung.
Which suits your home
The right choice depends on how many rooms you’re cooling and how much space you have outside:
- One room: a single split is the simple answer.
- Two to five rooms, close together: a multi-split, if one outdoor spot can reach them all.
- A flat: a multi-split keeps your request to the freeholder to one outdoor unit.
- A terraced or semi-detached house: planning rights allow one heat pump, so a second outdoor unit usually means an application. How planning works for air con.
- Rooms far apart: single splits can be easier, because each pipe run has a limit. Daikin’s five-room unit allows 25 metres for a room.
- Rooms on different floors: check the height limit. Daikin allows 7.5 metres between indoor units, or 15 metres if the outdoor unit sits below one of them.
- A room that can’t go without cooling: keep it on its own system, so a fault elsewhere won’t stop it.
- A large open-plan room: one outdoor unit can run two indoor units, which spreads the air better. Cooling an open-plan room.
One hot room doesn’t need a multi-split, and it may not need air con at all. When air con isn’t the answer.
Sources: the planning order and Daikin UK’s 5MXM table.
Cooling every room in a home
Cooling every room can mean a multi-split across five or six rooms, a ducted system, or several systems together. How to choose for a whole home.
How the costs compare
Two rooms on a multi-split often cost less than two single splits, because there’s one outdoor unit to buy and fit. For one room, a single split is the cheaper choice.
Several things can shift that:
- longer pipe runs, because each room needs its own
- a bigger outdoor unit, with a stronger fixing or base
- scaffolding, if the one outdoor spot is high up
- a planning application, if a second outdoor unit needs one
- servicing, which goes by how many units you have
Prices depend on your rooms, so every job is quoted after a survey. What sets the price.
Split system questions
How many rooms can one outdoor unit serve?
One home outdoor unit usually serves up to five rooms. Daikin, Hitachi, LG and Samsung all say five, and Mitsubishi Electric says six. Check the model, because smaller outdoor units serve fewer rooms.
If one indoor unit breaks, do the others stop?
The other indoor units usually keep running, because each has its own controls and pipe run. A fault in the shared outdoor unit stops every room, and a refrigerant leak can do the same.
Is a multi-split noisier?
A multi-split isn’t noisier overall, because one outdoor unit replaces several. That unit is bigger, so check its sound power figure. You may also hear flowing refrigerant in a switched-off room while others run, and Daikin says that’s normal. How loud air con is.
Is ducted better for a whole house?
Ducted air conditioning is neater, but it isn’t always better. It hides the units and serves several rooms, but it needs ceiling space and more building work. Ducted systems compared.