What’s involved in a professional installation
A proper air conditioning installation starts before anyone picks up a drill. A qualified engineer surveys the room or property, measures floor area, ceiling height and window exposure, and checks where an outdoor condenser can realistically be sited — factoring in noise regulations, neighbouring boundaries, and in many parts of London, conservation area or leasehold restrictions. Only after this survey should a system size and quote be confirmed.
On installation day, the work typically involves mounting the indoor unit, running refrigerant pipework and drainage to the outdoor condenser, wiring the electrical connection, and — critically — pressure testing and vacuuming the refrigerant circuit before the system is charged and commissioned. This last step is where corners get cut by unqualified fitters, and it’s the single biggest factor in whether a system runs reliably for the next decade or develops a slow refrigerant leak within a year or two.
Typical costs
A single-room wall-mounted split system typically costs £1,500–£2,800 fully fitted, depending on unit brand and installation complexity. Multi-split systems covering two to four rooms from one outdoor condenser generally run £3,000–£6,500. Ducted systems, which conceal the indoor unit in a ceiling or loft void and distribute air through short duct runs, typically start around £5,000 and can exceed £9,000 for larger properties. These figures assume straightforward access; conservation area properties, listed buildings, or difficult pipe runs can add to the cost.
The installation process, step by step
Most residential installations follow the same broad sequence: an initial survey and quote, confirmation of the system and unit positions, a scheduled installation day (usually one day for a single or dual system, up to two or three days for larger multi-split or ducted installations), commissioning and a demonstration of the controls, and a handover with warranty documentation. F-Gas regulations require anyone handling refrigerant to hold a valid F-Gas certification — always ask to see this before booking.
Common mistakes to avoid
The most frequent issue we hear about from homeowners who’ve had a poor experience isn’t the equipment — it’s undersizing. A system specified purely on floor area, without accounting for ceiling height, glazing, and sun exposure, often struggles to cool a room properly on the hottest days of the year, which is exactly when it matters most. The second most common issue is skipping planning checks; installing a visible condenser on a conservation-area property without checking permitted development rules first can mean an expensive repositioning job later. Finally, choosing an installer purely on price without confirming F-Gas certification and manufacturer accreditation risks both a poorly commissioned system and a voided warranty.
Maintenance after installation
A newly installed system still needs annual servicing to stay efficient and keep the manufacturer’s warranty valid — this typically includes a filter clean, coil inspection, refrigerant check, and drainage clearance. See our dedicated air conditioning servicing page for what a service visit involves.