Daikin 3MXM Multi-split

The Daikin 3MXM is the outdoor unit at the heart of a Daikin multi-split system: one condenser that drives up to three indoor units, so you can cool and heat a cluster of rooms without bolting a separate box to the wall for each. It is the tidy answer for a home that needs two or three rooms doing rather than one, and its real appeal is flexibility. Because the indoor units are chosen separately, you can put a designer Stylish or Emura where looks matter, a plain Perfera in the bedrooms and a value Sensira in the study, all running off the same 3MXM. On the 5.2 kW class it holds an A+++ cooling and A++ heating label on R32 refrigerant, with efficiency that is strong for a shared system.

The trade-offs are the ones every multi-split carries. One compressor serving several rooms is slightly less efficient than a dedicated single split per room, and it is a single point of failure: if the outdoor unit goes down, every connected room loses cooling and heating at once. The mix of indoor sizes is capped by the outdoor unit too, so the whole system has to be sized as one job rather than added to freely. It earns its place from two or three rooms upward, where one outdoor unit and one set of planning and wall-space headaches beats two or three. For that job, backed by Daikin's engineering and installer network, it is a sound choice.

The 3MXM is not a room unit you can see indoors. It is the outdoor condenser that sits at the centre of a Daikin multi-split system, and the M in the name stands for multi: one outdoor unit feeding refrigerant to as many as three indoor units through a single set of connections. You buy it alongside the indoor units you want, and an F-Gas certified engineer commissions the whole thing as one sealed system, so this is a fitted product priced per home, not something you plug in.

It suits a home that needs a small handful of rooms doing rather than one: a living room plus two bedrooms, or a couple of bedrooms and a home office. The case for a multi-split over separate single splits is space and tidiness. Instead of an outdoor box on the wall for every room, you have one, which matters on a flat, a terrace or any frontage where you do not want a row of condensers. The catch is that all those rooms then depend on one unit, so it is a genuine trade-off rather than a free win.

The 3MXM class covers up to three rooms; Daikin also sells a 2MXM for two, and 4MXM and 5MXM outdoor units for four and five. Within the 3MXM class the common sizes are the 4.0 kW 3MXM40, the 5.2 kW 3MXM52 and the 7.0 kW 3MXM68, and the figures here are for the mid 5.2 kW model. Whichever you choose, the best part is the freedom on the indoor side: a designer Stylish or Emura in the room you look at, a plain Perfera or value Sensira in the rooms you do not, plus multi-compatible ducted, cassette and floor units, all mixed on the same outdoor unit.

A multi-split is priced supplied and fitted, and the total scales with the number and type of indoor units, so there is no single shelf price. The 3MXM outdoor unit on its own is around £1,780 to £1,870 including VAT for the 5.2 kW model, but that is only one part. As a working guide, a complete two-room Daikin multi-split fitted tends to run from roughly £3,500 to £4,500, and a three-room system from about £4,500 to £6,500 or more, with the spread driven by whether you pick value Sensira and Perfera indoor units or the designer Stylish and Emura, and by how awkward the install is. Always work from a fixed written quote for your own home rather than a headline figure.

Running costs are kept low by the inverter, which modulates one compressor to the actual load rather than running flat out. On the 5.2 kW model the SEER of up to 8.50 and SCOP of up to 4.60 sit a little below a dedicated single split, the price you pay for sharing one outdoor unit, but they still earn an A+++ cooling and A++ heating label, and in heating the unit returns around four and a half units of heat for every unit of electricity, far cheaper than a plug-in heater delivering the same warmth. At the July 2026 Ofgem price cap unit rate of 26.11p per kWh, cooling a couple of rooms on a warm afternoon draws well under the outdoor unit's rated input once the rooms are at temperature. As a reverse-cycle air-to-air heat pump the system may qualify for the £2,500 Boiler Upgrade Scheme grant in England and Wales, but only if it replaces a fossil-fuel heating system and is fitted by an MCS-certified installer; comfort cooling added alongside a gas boiler does not qualify, and it is separate from the larger £7,500 air-to-water grant. Prices and rates correct as of July 2026; the energy price cap changes quarterly, so check current rates before budgeting.