The Short Answer
We'd buy a split that heats as well as cools: a single split for one room, a multi-split for several. A single split is about £1,500 to £3,500 fitted on our estimate. A multi-split runs several indoor units from one outdoor unit (up to 5 on Daikin's). It costs less than a separate system in each room and, in England and Wales, keeps a house that isn't detached to the one outdoor unit permitted development allows.
A split costs much less to run than a portable: 19.9p an hour against 35.5p at rated output, at the price cap rate. And in England and Wales a unit you also use for heating is usually permitted development, where a cooling-only one needs planning permission.
Which System Do You Need?
Answer four questions and it tells you which kind of system fits, what it's likely to cost fitted, and what that means for planning.
Which system do you need?
Single split, multi-split or portable
Four questions about your home, and what each choice means for cost and planning.
Our pick
A multi-split
About £3,500 to £6,500 fitted, on our estimate from published UK prices, with one outdoor unit.
- Daikin's multi-split outdoor units take up to 5 indoor units, so all 3 rooms can share one, and each room is still controlled on its own.
- Separate splits would need 3 outdoor units. In England and Wales, permitted development allows one on a house that isn't detached, counting any air source heat pump already there, so separate splits would need planning permission.
Separate splits for 3 rooms would be about £4,500 to £10,500 on the same price ranges (we assume never less than a multi-split, as OVO says separate systems cost more).
Planning
Probably permitted development in England and Wales: one outdoor unit is within the limit for your home, counting any air source heat pump already there, as long as it meets the size, position and noise rules and it isn't a listed building. In a conservation area, ask your council first. Scotland and Northern Ireland have their own rules. Check every rule.
Our recommendation from your answers, not a survey. An installer checks room sizes, pipe routes and where the outdoor unit can go.
How a Split System Works
A split system has an indoor unit in the room and an outdoor unit outside, with refrigerant pipes running between them. In summer the system moves heat from the room to the outside; reversed, it heats the room, which is why makers such as Daikin also call it an air-to-air heat pump. (For the grant, though, it has to be designed mainly to heat the whole home.)
The two units don't have to be side by side. Daikin's Perfera spec table allows a pipe run of up to 20 to 30 metres and a height difference of up to 15 to 20 metres between the units, depending on size. Every metre adds cost, though, and beyond 10 metres it needs extra refrigerant.
Single Split or Multi-Split?
A single split is one indoor unit and one outdoor unit, for one room. A multi-split connects several indoor units to one outdoor unit: Daikin's connects up to 5, each controlled separately, and you can add indoor units later. Daikin says one outdoor unit means less space used, less noise and lower installation and maintenance costs. Those are a manufacturer's claims, but the cost one stands up: OVO says a multi-split costs less than a separate system in each room.
| Rooms | Multi-split, fitted | Separate splits, fitted |
|---|---|---|
| 1 | £1,500 to £3,500 | The same |
| 2 | £3,500 to £5,000 | £3,500 to £7,000 |
| 3 | £3,500 to £6,500 | £4,500 to £10,500 |
| 4 | £3,600 to £6,500 | £6,000 to £14,000 |
| 5 | £6,000 to £9,500 | £7,500 to £17,500 |
Our estimate from OVO's and MyBuilder's published ranges (June 2026 and October 2026), the same sums as the cost estimator. Electrical upgrades and scaffolding are extra. For separate splits we multiply the one-room range by the rooms and assume they never come out below a multi-split, because OVO says separate systems cost more. OVO and MyBuilder give one price band for 2 to 4 rooms, so those rows overlap.
There's a planning reason to prefer a multi-split too. Permitted development in England and Wales allows one outdoor unit on a house that isn't detached, two on a detached house, and one for a whole block of flats, counting any air source heat pump already there. Three rooms of separate splits on a semi means three outdoor units and a planning application; a multi-split keeps it to one. Permitted development doesn't cover a unit on a listed building, and conservation areas have tighter rules on where the unit goes. Scotland and Northern Ireland have their own rules, so ask your council there.
The catch, in our view: every room depends on one outdoor unit, so if it fails, the whole house loses cooling at once. Each outdoor unit also takes only so many indoor units, so we'd size it for the rooms you might want, not just today's. Daikin's take up to 5; for six rooms or more, ask installers what their brand's larger units take.
Types of Indoor Unit
- Wall-mounted, high on the wall. The usual choice, and what the prices on this page are for.
- Floor-standing, low on the wall like a radiator, for rooms where a high wall unit won't go.
- Concealed ceiling (ducted), hidden above the ceiling with only grilles showing. Neat, but it needs ceiling space and can cost much more: OVO puts ducted systems at £8,000 to £15,000, MyBuilder at £4,000 to £6,000 or more.
On a multi-split you can mix them: Daikin lists wall, floor-standing and concealed ceiling units for the same outdoor unit.
Do Split Systems Work Well?
Yes, if it's sized and fitted properly. Daikin rates its 3.5kW Perfera at an EER of 4.63 (cooling out for each unit of electricity in), with a seasonal cooling SEER of 9.25 and heating SCOP of 5.20, both in the top energy label class, A+++. A portable such as Meaco's 12,000 BTU Cirro (about 3.5kW of cooling) draws about 1.8 times the power for similar rated cooling, because the whole machine sits in the room and vents its hot air out through a hose: about 756W against 1,350W. At the Great Britain price cap rate of 26.32p per kWh, that's 19.9p an hour against 35.5p at rated output. Our running costs guide works through it at today's electricity price.
The Downsides
- It has to be fitted. Connecting the refrigerant circuit needs an F gas qualified installer by law, so it isn't a DIY job.
- Indoor noise. Indoor units can be noisier than other heat pumps, the Energy Saving Trust says. Daikin rates its 2.5kW Perfera indoor unit at 19 dB(A) on its silent setting, 25 on low and 41 on high. In a bedroom, ask for a quiet mode.
- The outdoor unit needs a spot that meets the planning rules on noise, size and position. Our planning guide has a checker.
- No hot water from most systems (Daikin's Multi+ is one that adds a hot water tank), so on its own it won't replace a boiler.
- Cost. A portable needs no fitting; a split starts at about £1,500.
Which We'd Choose
- One bedroom or home office: a single wall-mounted split that heats too, with a quiet or silent mode. Daikin rates its 2.5kW Perfera indoor unit at 19 dB(A) on silent.
- Two to five rooms, now or later: one multi-split, with an outdoor unit sized for the rooms you might add, not just today's. It's cheaper than separate systems and, in England and Wales, keeps a house that isn't detached within permitted development's one outdoor unit.
- A detached house with several rooms: in England and Wales, permitted development allows two outdoor units, so we'd think about splitting the rooms across two systems. It costs more than one multi-split, but if one outdoor unit fails, only half the house loses cooling.
- A flat: in England and Wales, permitted development allows one outdoor unit for the whole block, so check whether there's one already before you buy anything.
- A few hot weeks a year in one or two rooms, and you don't need it to heat: we'd buy a portable instead (one per room), which needs no installer.
- Replacing your heating for the whole home: that's an air-to-air heat pump, and it's worth reading our air-to-air guide first, because of the grant to come and the hot water it won't provide.
The Mistakes to Avoid
- A separate split in every room on a semi or terrace. Each needs its own outdoor unit, and the second takes you outside permitted development in England and Wales.
- An outdoor unit sized only for today. You can add indoor units later, but only up to what the outdoor unit takes.
- Cooling only. It needs planning permission in England and Wales (the rule is about use, so a unit that could heat but is only ever used to cool counts the same), and it won't heat in winter.
- Ducted when you don't need it. It looks neat, but it needs ceiling space, and on OVO's prices it costs far more (see above).
- Pricing the unit, not the job. A split unit on a shopping site is only part of it: the installer, pipework, electrics and making good come on top.
What a Split System Costs
The unit is only part of it. MyBuilder puts a split unit at £500 to £1,500 and the installation at £500 to £1,310 on top. So the cheap units you'll see on shopping sites aren't the price you pay: add the installer, the pipework, the electrics and making good. For a fitted single split, MyBuilder's own figure is £1,500 to £3,000 and OVO's goes up to £3,500, so about £1,500 to £3,500 all told.
A split system designed mainly to heat your whole home (MCS excludes systems optimised for cooling) that replaces fossil fuel or electric heating counts as an air-to-air heat pump. The Boiler Upgrade Scheme lists £2,500 off one in England and Wales, though it can't be claimed yet. Our air-to-air heat pump guide has the details, and the installation cost guide prices your job.
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