Multi-split systems
Cool and heat several rooms from a single outdoor unit. Tidier than multiple separate systems, and you can mix wall, floor, cassette and ducted indoor units on one condenser.
How to choose an air conditioning system for your home
Frequently asked questions
How many rooms can one outdoor unit serve? +
Most residential multi-split outdoor units support between two and five indoor units, and some ranges (such as Mitsubishi Electric MXZ-F) go to six. Each indoor unit is controlled separately, so different rooms can be different temperatures, or off entirely.
Why is the outdoor unit smaller than the total of the indoor units? +
This is called diversity. Because you rarely run every room at full cooling at the same moment, the outdoor unit is sized below the combined capacity of the indoor units, which keeps it smaller, cheaper and quieter. The trade-off is that on the very hottest days, if several rooms call for maximum cooling at once, performance can dip slightly.
Can I mix different indoor unit types? +
Yes. One of the big advantages of a multi-split is that you can put a wall unit in a bedroom, a floor console in a room with lots of glazing and a ceiling cassette in an open-plan space, all on the same outdoor unit.
Multi-split or several single splits, which is better? +
A multi-split wins where outdoor space is tight or you want one condenser instead of several, and it usually looks tidier. Separate single splits can be cheaper per room and mean a fault in one system does not affect the others. It comes down to how many rooms, your outdoor space and budget.
Can I add a room later? +
Often yes, if the outdoor unit was specified with spare capacity and connection points. If it was sized tightly for the original rooms, adding a head later may mean a larger outdoor unit. Tell your installer at the design stage if you might expand.
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Multi-split air conditioning, explained
A multi-split cools and heats several rooms from a single outdoor condenser, with a separate indoor unit in each room. It is the tidy answer to whole-home comfort: instead of a row of outdoor units, you have one, and each room still gets its own temperature and controls. Most residential systems run two to five indoor units on one outdoor unit, some up to six.
The real flexibility is that you can mix indoor formats on the same system: a discreet wall unit in a bedroom, a floor console under a window, a ceiling cassette in an open-plan kitchen. Current UK ranges from Daikin, Mitsubishi Electric, Fujitsu, LG and Samsung all use R32 and are reverse-cycle, so they heat as well as cool.
What to expect
- 2 to 5 units
- Indoor units per outdoor unit (up to 6)
- 1 outdoor unit
- For the whole system
- £2,800 to £7,000
- Supplied and fitted, 2 to 4 rooms
- R32
- Refrigerant on current ranges
Sizing, cost and how it compares
Sizing and diversity. Each room is heat-load sized for its own indoor unit (our BTU calculator gives you a rough per-room figure to start from), then the outdoor unit is chosen using diversity: below the sum of the indoor capacities, on the basis that not every room runs flat out at once. This keeps the outdoor unit compact and quiet. Oversizing the whole system is a common and costly mistake, so a good design meets your peak demand while spending most of its life modulating gently.
Install and cost. Every indoor unit needs its own refrigerant pipe run back to the single outdoor location, so pipework and route planning are a bigger part of the job than a single split, and cost scales with the number of heads. As a guide, budget roughly £2,800 to £4,500 for two rooms and £3,500 to £7,000 for three to four, supplied and fitted, with each extra head adding around £700 to £1,500. These are secondary-sourced bands, so get two or three installer quotes.
Multi-split, single splits or ducted. Choose a multi-split for two or more rooms where outdoor space is limited. Separate single splits can cost less per room and isolate faults. Ducted hides everything for the tidiest finish but costs the most and suits a renovation or new build.
Prices and running costs correct as of July 2026. The energy price cap changes quarterly, so check current rates before budgeting.
Multi-split systems we rate
Daikin 3MXM Multi-split
★★★★★ ★★★★★ 4.35.2 kW class · up to 3 rooms · R32 · A+++/A++
outdoor unit only, 3MXM52A9 5.2 kW, inc VAT, out of stock £1,944.00Mitsubishi Electric MXZ Multi-split
★★★★★ ★★★★★ 4.35.4 kW class · up to 6 rooms · R32 · A+++/A++
supply only, MXZ-2F42VF4 with two 2.5 kW wall units £2,278.03Related guides
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