Choosing a system
What’s the difference between single-split and multi-split?
A factual comparison of single-split and multi-split air conditioning for UK homes: how each works, the trade-offs, and which questions to ask on a survey.
Last reviewed 2 min read
Single-split
A single-split system pairs one indoor unit with one outdoor unit. It’s the most common choice for a single room such as a bedroom, home office or living room.
Because each room has its own outdoor unit, a fault only affects that room, and you can add more rooms later without changing what’s already installed.
Multi-split
A multi-split system connects several indoor units, typically two to five, to one outdoor unit. It’s often considered when several rooms need cooling or heating and there’s only one sensible place outside for a unit.
The outdoor unit is sized for the rooms it serves, so adding a room later may not be possible. If the outdoor unit fails, every room on it is affected.
Side-by-side comparison
| Single-split | Multi-split | |
|---|---|---|
| Indoor units per outdoor unit | One | Usually two to five |
| Outdoor space needed | One unit per room | One larger unit |
| If the outdoor unit fails | One room affected | All connected rooms affected |
| Adding rooms later | Straightforward | Limited by the outdoor unit’s capacity |
| Cost for one room | Lower | Not usually used for one room |
| Cost for several rooms | Can be higher overall | Often lower than separate systems |
What decides which suits your home
- How many rooms you want to cool or heat, now and in future.
- Where outdoor units can go, and how visible they would be.
- How far refrigerant pipes would have to run between rooms and the outdoor unit.
- The capacity of your electrical supply and consumer unit.
An installer will assess these on a survey. If you’re unsure, send an enquiry and ask for both options to be priced.
Common questions
- Is multi-split cheaper than several single-splits?
- For three or more rooms it often is, because there’s one outdoor unit and less external work. For two rooms the difference can be small, so it’s worth asking for both to be quoted.
- Can I add another room to a multi-split later?
- Only if the outdoor unit has spare capacity and spare connections. If you might add rooms, tell the installer at the survey so they can size the outdoor unit for it.
This guide is general information, not professional planning, electrical or financial advice. Check the details for your property with the council and a qualified installer.