Air conditioning installation: what happens on the day
Half the hesitation about installed air conditioning is simply not knowing what you're signing up for — how much drilling, how much mess, how long the house is upside down. The honest answer: for a single-room split, it's half a day to a day, one hole through the wall, and less disruption than having a washing machine plumbed in. Here's the whole journey, so nothing on the day is a surprise.
Before the day: the survey
A good installer surveys before quoting final numbers — free surveys are common and worth taking. They'll confirm the unit size (they should measure and calculate, not eyeball — you can sanity-check them against our calculator), agree positions for the indoor and outdoor units, trace the pipe run and condensate drain route, check your consumer unit has capacity for a dedicated circuit, and — since the May 2025 rules — run the MCS 020 noise assessment that keeps the install within permitted development (details here). Ask three things while they're there: exactly what's included in the price, who does the electrical work, and what the warranty covers (unit and workmanship separately).
On the day, step by step
- Indoor unit mounting (first hour). A bracket goes on the wall, high on the agreed spot. The only structural work of the day happens now: a single ~65 mm hole drilled through the external wall behind or beside the unit, angled slightly down for drainage. It's loud for a few minutes and produces some dust — the installer should sheet the area, but move anything precious yourself.
- Outdoor unit siting. The condenser sits on a wall bracket or ground-level feet, on anti-vibration mounts, at the surveyed position. Upper-floor or flat-roof positions may involve ladders or access equipment agreed at survey.
- Pipework and cabling. Insulated copper refrigerant pipes, the condensate drain and cabling run between the two units, usually in white trunking down the external wall — ask to see the trunking route at survey if appearance matters to you. Interior pipe runs are possible but add time and making-good.
- Electrical connection. A dedicated circuit from your consumer unit — either the installer's electrician or your own, agreed beforehand. If your consumer unit is full or dated, this is where pre-agreed extras appear; a good quote flagged it at survey.
- Vacuum and pressure test — the step that separates professionals from cowboys. Before any refrigerant flows, the pipework is evacuated with a vacuum pump and held to prove there are no leaks and no moisture. It takes time (30+ minutes) and skipping it quietly wrecks systems within a couple of years. If you see the vacuum pump come out, you hired well.
- Refrigerant release and commissioning. The engineer opens the valves (this is the F-Gas certified part — handling refrigerant is what the legal certification exists for), runs the system in both cooling and heating modes, checks temperatures and the condensate drain, and walks you through the controls.
Multi-room installs scale the same steps: roughly a day for two rooms, two days for three or four, since the outdoor unit and its electrics are shared.
What to prepare (fifteen minutes the night before)
- Clear the wall areas for both units and a path between them, plus access to the consumer unit.
- Decide parking — installers arrive with pipe benders, vacuum pumps and a condenser; a van outside matters.
- Dust sheets protect floors, but move electronics and anything irreplaceable out of the work room.
- Dogs and drilling don't mix — plan accordingly.
The paperwork to keep — this part matters
Before the installer leaves, you should hold: the commissioning certificate (system tested and performing to spec), the F-Gas documentation recording the refrigerant type and charge, the MCS 020 noise assessment (your permitted-development evidence), the electrical certificate for the new circuit, and the warranty terms — manufacturer's on the unit (often 3–7 years, sometimes conditional on annual servicing) and the installer's on workmanship. File all of it: it's what a buyer's solicitor asks for when you sell, what a neighbour dispute never gets past, and what keeps the warranty alive.
Aftercare in one paragraph
Clean the indoor unit's filters every few weeks in heavy use (they slide out; rinse, dry, replace — five minutes), keep leaves off the outdoor unit, and book an annual service (£70–£120) which typically keeps the manufacturer warranty valid and the efficiency at spec. That's the whole maintenance burden. Running costs, if you're still weighing the decision, are in the running costs guide.
Ready for the survey stage? Get up to three free quotes from F-Gas certified installers — and now you know exactly what a professional job looks like, you'll judge the quotes better than most buyers ever do.
Quick answers
How long does air conditioning installation take?
Half a day to a full day for a single-room split; add roughly half a day per additional indoor unit for multi-splits. Long pipe runs, difficult access or consumer unit work extend it — all things a survey identifies in advance.
How messy is the installation?
One drilled hole's worth of dust, contained with sheeting, plus some trunking work outside. No floors up, no walls open. It's among the least disruptive installations a home can have relative to what it delivers.
Can the installation be done in winter?
Yes — and it's often cheaper and faster to book, since demand craters after summer. Installers commission the heating mode instead. Buying in November for next July is the seasoned move (and you get a winter of cheap room heating immediately).