Multi-Split AC: Cool Multiple Rooms from One Outdoor Unit

What Is Multi-Split Air Conditioning?

A multi-split air conditioning system is a type of split system that connects multiple indoor units to a single outdoor condensing unit. Instead of installing a separate outdoor unit for every room you want to cool, a multi-split system uses one outdoor unit to serve two, three, four or even five indoor units in different rooms. Each indoor unit operates independently with its own thermostat and remote control, so you can set different temperatures in different rooms and turn individual units on or off as needed.

Multi-split systems are one of the most popular AC solutions for London homes and flats, and for good reason. They provide flexible, room-by-room climate control with a minimal outdoor footprint — a critical advantage in London where external wall space and balcony space are often limited, and freeholders may restrict the number of outdoor units on a building.

At London AC Pro, we design and install multi-split systems from all leading brands including Daikin, Mitsubishi Electric, Samsung, LG, Fujitsu and Toshiba. We are F-Gas certified and serve all 32 London boroughs. This guide covers everything you need to know about multi-split AC for your London property.

How Does Multi-Split AC Work?

The working principle is the same as a standard single-split system. Refrigerant circulates between the indoor and outdoor units, absorbing heat from inside the room and releasing it outside. The difference is that a multi-split outdoor unit has a larger compressor and the capacity to supply refrigerant to multiple indoor units simultaneously.

Key Components

• Outdoor unit (condenser) — sits outside on a wall bracket, balcony or flat roof. Contains the compressor, condenser coil and fan. Larger than a single-split outdoor unit but typically only 20–30% bigger, not double the size.
• Indoor units — wall-mounted, ceiling cassette, ducted or floor-standing units in each room. Each has its own evaporator coil, fan and thermostat.
• Refrigerant pipework — copper pipes connecting the outdoor unit to each indoor unit, carrying refrigerant between them.
• Branch joints — special fittings where the pipework from the outdoor unit splits to serve each indoor unit.
• Communication wiring — data cables between units for system control and monitoring.

Independent Control

Each indoor unit is controlled independently via its own remote control, wall-mounted controller or smartphone app. You can cool the living room to 22°C while keeping the bedroom at 24°C, or turn off the bedroom unit during the day when nobody is in it. The outdoor unit's inverter compressor adjusts its speed to match the total demand from all active indoor units, providing excellent energy efficiency.

How Many Rooms Can a Multi-Split System Cover?

The maximum number of indoor units depends on the brand and the capacity of the outdoor unit:

• Daikin — up to 5 indoor units on their MXM multi-split outdoor units
• Mitsubishi Electric — up to 6 indoor units on their MXZ range
• Samsung — up to 5 indoor units on their multi-split systems
• LG — up to 5 indoor units on their Multi F range
• Fujitsu — up to 5 indoor units on their AOYG multi-split range
• Toshiba — up to 5 indoor units on their multi-split range

For most London homes and flats, two to four indoor units is the sweet spot. If you need to cool more than five rooms, a VRF system is likely the better solution — read our VRF guide for details.

Pros of Multi-Split AC

1. One outdoor unit for multiple rooms — the biggest advantage. Instead of cluttering the exterior with multiple condensers, you have just one compact outdoor unit.
2. Independent room control — each room has its own thermostat and can be set to a different temperature or turned off independently.
3. Mix and match indoor unit types — you can combine wall-mounted units in bedrooms with a ceiling cassette in the living room and a ducted unit in the hallway, all on the same system.
4. Energy efficient — modern inverter-driven multi-split systems from Daikin and Mitsubishi achieve A++ and A+++ energy ratings.
5. Heating and cooling — all multi-split systems operate as heat pumps, providing both heating and cooling from the same system.
6. Quiet operation — premium indoor units run at just 19–22 dB(A).
7. Smart control — Wi-Fi connectivity and smartphone app control is standard on all major brands.
8. Space saving — fewer outdoor units means less external space required.

Cons of Multi-Split AC

1. Longer pipework runs — because all indoor units connect to a single outdoor unit, pipework runs are often longer than with individual single-split systems. This can increase installation cost and complexity.
2. Single point of failure — if the outdoor unit develops a fault, all indoor units are affected. With individual single-split systems, a fault in one outdoor unit only affects one room.
3. Higher upfront cost than a single-split — naturally, a multi-split system costs more than a single-split because it includes multiple indoor units and a larger outdoor unit. However, it is typically cheaper than installing equivalent single-split systems for each room.
4. Simultaneous mode limitation — most multi-split systems (unlike VRF) require all indoor units to be in the same mode at the same time — either all cooling or all heating. You cannot cool the bedroom while heating the living room. In practice, this is rarely an issue for residential use.
5. Installation complexity — multi-split installations require more skilled design and installation than a simple single-split. Pipe sizing, branch joint placement and refrigerant charge calculations must be done correctly. Always use an experienced, F-Gas certified installer.

Multi-Split vs Ducted: Which Is Right for You?

Ducted air conditioning is the other main option for cooling multiple rooms. Here is how the two compare:

Aesthetics

Ducted systems are completely concealed within the ceiling, with only discreet vents visible. Multi-split systems have visible indoor units on the wall or ceiling in each room. If you want invisible cooling, ducted is the way to go — but it requires adequate ceiling void space.

Individual Control

Multi-split systems offer true independent control of each room. Basic ducted systems cool the entire zone to one temperature. However, zoned ducted systems with motorised dampers can provide room-by-room control at a higher cost.

Installation

Multi-split is generally easier and less disruptive to install, as it does not require extensive ductwork. Ducted systems need a ceiling void of at least 250mm and significant building work to install the duct network.

Cost

Multi-split systems are typically less expensive to install than equivalent ducted systems, particularly in existing properties where ductwork would need to be retrofitted.

Our Recommendation

For most London homes and flats, a multi-split system offers the best balance of performance, flexibility and cost. Ducted systems are ideal for new-builds, major refurbishments, or properties where the aesthetic of completely hidden cooling is a priority.

Multi-Split AC Cost Guide for London

Here are typical installed prices for multi-split systems in London, based on mid-range to premium brands:

• 2 rooms (dual-split) — £3,499 to £4,500
• 3 rooms (tri-split) — £4,999 to £6,500
• 4 rooms (quad-split) — £6,500 to £8,000
• 5 rooms (penta-split) — £7,500 to £9,500

Prices include supply of equipment, installation, pipework, electrical connection, F-Gas commissioning and a workmanship guarantee. For a detailed cost breakdown and factors that affect pricing, read our AC Installation Cost Guide for London 2026.

Popular Multi-Split Configurations for London Homes

Based on our experience, here are the most common multi-split configurations we install in London:

Two-Bedroom Flat

A dual-split system with wall-mounted units in the bedroom and living room. The outdoor unit sits on the balcony or rear wall. This covers the two main living spaces where cooling matters most.

Three-Bedroom House

A tri-split or quad-split system with units in the master bedroom, second bedroom and main living area. Some customers add a fourth unit in a home office or top-floor room.

Loft Conversion + Bedrooms

Loft conversions are notoriously hot in summer. A multi-split system with one unit in the loft and one or two in the bedrooms below is a very popular configuration.

Choosing the Right Brand for Your Multi-Split

All the major brands we install — Daikin, Mitsubishi, Samsung, LG, Fujitsu and Toshiba — offer excellent multi-split systems. For a detailed comparison, see our blog post: Daikin vs Mitsubishi vs Samsung: Which AC Brand Is Best?

Get a Free Multi-Split Quote from London AC Pro

If you are considering multi-split air conditioning for your London home or flat, the first step is a free, no-obligation site survey. Our F-Gas certified engineers will visit your property, assess the rooms you want to cool, recommend the best system configuration and brand, and provide a transparent, fully itemised quote. We install multi-split systems across all 32 London boroughs — from studio flats to five-bedroom houses. Call us on 07301 010244 or request your free quote online.