Air con
Single-room or multi-room air conditioning — which do I need?
3 min read · Last updated · Reviewed for accuracy before publishing
It comes down to how many rooms you genuinely want to control and how they're laid out. A single-room (single-split) system is one indoor unit and one outdoor unit — simplest, ideal if you mainly want one space sorted. A multi-room (multi-split) system runs several indoor units from one outdoor unit — tidier outside and great when you want a few rooms independently controlled. But multi-split isn't automatically cheaper or better: BestBuilders puts a single room at £1,500–£3,000, two rooms at £2,800–£4,500 and three to four at £3,500–£7,000. We size it to your actual rooms.
When single-room wins
If it's really one space you care about — the master bedroom, the home office, the hot living room — a single-split is the simplest to install and service, and BestBuilders' 2026 figure for one is £1,500–£3,000. Many homes start here, and often that's all they ever need. Adding a second single-split later is straightforward too.
When multi-room wins
Want several rooms cooled and independently controlled, and prefer just one unit on the outside wall? A multi-split shares one outdoor unit across multiple indoor heads — neater, and BestBuilders' 2026 figures are £2,800–£4,500 for two rooms and £3,500–£7,000 for three to four. Each room sets its own temperature. It's the tidy, whole-upstairs answer.
The honest catch
Multi-split isn't always the economy option people assume, so we price it against separate single-room systems. With one outdoor unit serving every room, if it fails every room loses cooling at once; separate systems mean a fault never takes out the whole house. We'll tell you where your home sits on that line.
“Multi-split is not automatically the economy option — price it against separate single-room systems, and remember one outdoor unit failing takes out every room it serves.”
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Sources
Datum's engineers install and service boilers, air conditioning, heat pumps and plumbing across South Hertfordshire and London. Guides are written from real jobs, not brochures.