Glossary · Air conditioning
What is multi-split air conditioning?
Multi-split air conditioning connects two or more indoor units to a single outdoor unit. Each indoor unit is controlled on its own, so rooms can be heated or cooled separately without a separate outdoor unit for every room. It suits homes with several rooms that need individual temperature control.
Key points
- One outdoor unit serves several indoor units, and each indoor unit can be controlled independently.
- The number of indoor units depends on the make and model. Daikin's Multi range connects up to five, and Mitsubishi Electric's range spans two to eleven.
- Fewer outdoor units means less wall or garden space used and, Daikin says, less noise and quicker installation than several separate systems.
- Indoor units must match the outdoor unit. Capacity is chosen in kW for each room.
- Refrigerant work is regulated, so installation needs a person with the correct F gas qualification.
How multi-split air conditioning works
A multi-split system connects multiple indoor units to a single outdoor unit. Mitsubishi Electric says this lets you control the temperature in several rooms independently.[1]Mitsubishi Electric, Multi-Split Air Conditioning A split system, by contrast, links only one indoor unit to one outdoor unit.[1]Mitsubishi Electric, Multi-Split Air Conditioning
The outdoor unit holds the compressor. Refrigerant pipes run from it to each indoor unit, which can be wall-mounted, floor-standing or concealed in a ceiling, depending on the model.[2]Daikin UK, Daikin Multi air conditioner: Multi-room heating and cooling Daikin says each indoor unit is controlled separately, and that you can combine units of different types and colours to suit each room.[2]Daikin UK, Daikin Multi air conditioner: Multi-room heating and cooling
How many rooms, and what to check
The limit depends on the manufacturer and the range.
| Maker and range | Indoor units on one outdoor unit |
|---|---|
| Daikin Multi | Up to five |
| Mitsubishi Electric multi-room range | Between two and eleven |
| Mitsubishi Electric MXZ-F series | Up to six |
These come from the manufacturers’ own product pages.[1]Mitsubishi Electric, Multi-Split Air Conditioning[2]Daikin UK, Daikin Multi air conditioner: Multi-room heating and cooling The indoor and outdoor units must be a compatible combination, so the installer checks the maker’s combination table. Each room also needs its own capacity in kW, based on floor area, ceiling height, insulation and how the room is used.[4]Daikin UK, Air Conditioner Size Guide: Find the Right Unit Daikin says a multi-split is a good choice where, for example, a lounge needs 3.5 kW and a bedroom 2 kW, and that it can be more efficient than two stand-alone systems.[4]Daikin UK, Air Conditioner Size Guide: Find the Right Unit
Example
Gurpreet has a three-bedroom house in Bradford. The loft bedroom and the front living room both get hot in summer, and the back bedroom is fine. Two single splits would put two outdoor units on the walls. A multi-split serves both rooms from one outdoor unit and leaves a spare connection for later.
Daikin says fewer outdoor units mean less space used and less noise, and that you can start with what you need today and add more indoor units later.[2]Daikin UK, Daikin Multi air conditioner: Multi-room heating and cooling Mitsubishi Electric says multi-split saves space and is more pleasing to look at because you need fewer outdoor units.[1]Mitsubishi Electric, Multi-Split Air Conditioning BASI lists two-room and three-room fitted packages on its air conditioning page, with the exact quote confirmed after a free survey.[6]BASI Heating, Air conditioning, supplied and fitted
What people get wrong
A common assumption is that a multi-split is always cheaper or better than separate units. It is better where several rooms need independent control. Mitsubishi Electric recommends a split system for a single room, which keeps cost and installation simpler.
That advice is in Mitsubishi Electric’s guide.[3]Mitsubishi Electric, How to choose the right home air conditioning
The second mistake is thinking you can add any indoor unit later. The limit is set by the outdoor unit and its combination table, so plan for future rooms at the quote stage. Installation also needs a person with the right F gas qualification. GOV.UK says it is against the law to work with F gas without the correct qualification.[5]GOV.UK, Qualifications to work with F gas See refrigerant and air conditioning servicing for aftercare.
The bottom line
Multi-split air conditioning puts one outdoor unit behind several indoor units, with separate control in each room. It reduces the number of outdoor boxes and suits homes where more than one room needs cooling or heating. Check how many indoor units your chosen outdoor unit can take and have it fitted by a qualified installer.
Common questions
How many rooms can a multi-split system serve?
It depends on the make and model. Daikin says its Multi range connects up to five indoor units to one outdoor unit. Mitsubishi Electric says its multi-room systems connect between two and eleven. Check the manufacturer's combination table.
Can I add rooms to a multi-split later?
Often yes. Daikin says you can start with the indoor units you need now and add more to the same outdoor unit later, within the limit of the model you chose.
Is multi-split better than several single splits?
Mitsubishi Electric says multi-split suits premises where you need to heat more than one room independently, and that it saves space and looks tidier because there are fewer outdoor units. For a single room, a split system is the better fit.
Who can install a multi-split system?
Someone with their own F gas qualification. GOV.UK says it is against the law to install or service air conditioning that contains F gas without the correct qualification.
Sources
We cite the original source for every figure: government, regulators, standards bodies and manufacturers' own documents. Each one shows the date we last checked it.
- Mitsubishi Electric. Multi-Split Air Conditioning. Checked 11 November 2026. ↩
- Daikin UK. Daikin Multi air conditioner: Multi-room heating and cooling. Checked 11 November 2026. ↩
- Mitsubishi Electric. How to choose the right home air conditioning. Checked 11 November 2026. ↩
- Daikin UK. Air Conditioner Size Guide: Find the Right Unit. Checked 11 November 2026. ↩
- GOV.UK. Qualifications to work with F gas. Checked 11 November 2026. ↩
- BASI Heating. Air conditioning, supplied and fitted. Checked 11 November 2026. ↩