One of the first things people ask before booking an air conditioning installation is how long the whole thing actually takes. Fair question. Nobody wants engineers camped out in their living room for a week if it can be done in a day.
The honest answer is: it depends on the system. A straightforward wall-mounted split in a bedroom can be done in a single day. A full commercial VRF fit-out across multiple floors could take weeks. Here's a realistic breakdown based on what we see on site every day.
Installation Times by System Type
| System Type | Typical Time | Best For |
|---|---|---|
| Wall-mounted single split (back-to-back) | 4-8 hours (1 day) | Bedrooms, home offices, small shops |
| Wall-mounted single split (long pipe run) | 1-2 days | Rooms away from external walls |
| Multi-split (2 indoor units) | 1-2 days | Flats, small offices |
| Multi-split (3-5 indoor units) | 2-4 days | Larger homes, multi-room offices |
| Ceiling cassette (single) | 2 days | Shops, restaurants, open-plan offices |
| Ceiling cassette (twin) | 3 days | Larger commercial spaces |
| Ducted split system | 3-5 days | Whole-house cooling, premium offices |
| VRF/VRV commercial system | 1-4 weeks | Multi-storey buildings, large offices |
These timelines assume a fairly standard installation with decent access. The reality is that every job has its quirks, and some of those quirks add time.
What Actually Happens During Installation
If you've never had air conditioning fitted before, it helps to know what the engineers are actually doing all day. Here's a stage-by-stage breakdown for a typical wall-mounted split system.
Stage 1: Setup and Protection (30-60 minutes)
Dust sheets go down, furniture gets moved, tools come in. We protect your floors and walls before any drilling starts. It might seem like a slow start, but skipping this step means cleaning bills later.
Stage 2: Core Drilling (60-90 minutes per hole)
This is the noisy bit. We drill through the external wall to run the refrigerant pipes, power cable, and condensate drain between the indoor and outdoor units. A standard cavity brick wall takes about 20-30 minutes per penetration. Reinforced concrete or solid stone walls need diamond drilling, which can push that to over an hour per hole.
Stage 3: Indoor Unit Mounting (1-2 hours)
The backplate gets fixed to the wall, pipes are routed and connected, and the indoor unit is hung in place. Sounds simple, but getting the unit perfectly level and ensuring the condensate drain has the right fall takes care.
Stage 4: Outdoor Unit Installation (1-2 hours)
The compressor unit goes on wall brackets, a ground-level stand, or a flat roof. Ground-level is quickest. Wall-mounted at height needs extra fixings and possibly scaffolding. Roof-level placements can add half a day just for access equipment.
Stage 5: Pipe and Electrical Connections (2-3 hours)
Refrigerant lines get flared and connected, the condensate drain is routed, and the electrical supply is wired in. If the unit needs a dedicated circuit back to your consumer unit (anything over about 3.5kW usually does), this stage takes longer.
Stage 6: Pressure Testing and Vacuum (1 hour)
We pressurise the system with nitrogen to check for leaks, then pull a deep vacuum to remove all air and moisture from the pipework. This step is non-negotiable. Skipping it leads to compressor failure down the line.
Stage 7: Commissioning and Handover (1-2 hours)
The system gets charged with refrigerant, switched on, and tested in both cooling and heating modes. We check airflow, temperatures, and drainage. Then we walk you through the remote control, set up any WiFi features, and register your manufacturer warranty.
What Makes an Installation Take Longer
In over 20 years of fitting air conditioning across London, these are the things that consistently add time to a job.
Wall Construction
Timber stud walls are the quickest to work through. Standard cavity brick is straightforward. Solid stone or reinforced concrete needs diamond drilling, which can triple the time per penetration. Older London properties often have surprisingly thick, hard walls that slow everything down.
Pipe Run Distance
A back-to-back installation (indoor unit on an external wall, outdoor unit directly behind it) is the fastest setup. Every extra metre of separation between the units adds time for pipe routing, fixings, insulation, and additional refrigerant charge. Running pipes through ceiling voids or loft spaces also means fire-stopping at each penetration point.
Electrical Requirements
Small units (under 3.5kW) can often connect to an existing ring main through a fused spur. Larger units and multi-split systems need a dedicated circuit run back to the consumer unit. If your board is full, a new consumer unit or secondary distribution board might be needed. That's electrician time on top of the AC installation.
In England and Wales, all fixed electrical work in homes falls under Part P of the Building Regulations. The electrical hookup should be done by a Part P-certified electrician or an installer who can self-certify.
Condensate Drainage
The simplest route is a gravity drain straight through the wall to the outside. When the indoor unit is on an internal wall or in a basement where gravity doesn't work, a condensate pump is needed. Pumps add installation time and require testing to make sure they run quietly.
Access and Height
Ground-level outdoor units are quick to position. High-level or rooftop placements need scaffolding, access towers, or cherry pickers, adding hours or a full extra day. In London, scaffold erection often needs a pavement licence if it encroaches on a public footpath.
Occupied Buildings
Working in an occupied office means restricted hours, furniture shuffling, noise limitations, and coordination around meetings and daily routines. A job that would take one day in an empty space might stretch to two in a busy office.
Weather
External work (outdoor unit positioning, wall drilling, scaffold work) can be delayed by heavy rain, high winds, or snow. We don't cancel for a bit of drizzle, but safety comes first for anything at height.
Equipment Lead Times (Before Installation Even Starts)
Installation time is only part of the picture. You also need to factor in how long it takes to get the equipment.
| Equipment Type | Typical Lead Time |
|---|---|
| Standard wall-mounted splits (Daikin, Mitsubishi, Fujitsu) | 1-2 weeks |
| Multi-split systems | 2-4 weeks |
| VRF/VRV systems | 4-8 weeks |
| Specialist units (water-cooled, precision cooling) | 6-10 weeks |
During peak summer months (June-August), lead times stretch because everyone orders at once. If you know you want air conditioning installed for summer, booking in March or April gives you the best availability and avoids the rush.
UK-Specific Factors That Can Add Weeks
Planning Permission
Most domestic AC installations fall under permitted development and don't need planning permission. But if your property is in a conservation area, is a listed building, or the outdoor unit would be visible from a public highway, you may need approval from your local council. That process takes 8-12 weeks on top of everything else.
Listed Buildings
Listed Building Consent is almost always required for any alteration, even internal ones, that could affect the building's character. External condensers on listed facades are a particular challenge. We've handled these jobs with water-cooled systems that eliminate the need for an outdoor unit entirely, or by using existing service routes to avoid new penetrations. Either way, add weeks for the consent process before any physical work starts.
Leasehold and Freeholder Consent
If you live in a flat, you'll typically need written permission from your freeholder or management company before an outdoor unit can be installed on the building's exterior. Some are quick to respond, others take months. Start this conversation early.
A Real Timeline: From Enquiry to Cool Air
Here's what a typical residential project looks like from start to finish.
| Stage | Duration |
|---|---|
| Initial enquiry and quote | 1-3 days |
| Free site survey | Booked within 1 week |
| Quote acceptance and deposit | Same day to 1 week |
| Equipment ordering and delivery | 1-3 weeks |
| Installation day(s) | 1-2 days (single split) |
| Total: enquiry to cool air | 2-5 weeks |
For commercial projects with VRF systems, design work, building management integration, and multiple zones, the realistic timeline is 8-16 weeks from first meeting to handover.
How to Speed Things Up
- Book early. Spring installations avoid the summer rush and give you the best choice of dates.
- Get your electrics checked. If you already know your consumer unit has spare capacity, that's one less variable on installation day.
- Clear the work area. Moving furniture, clearing access to loft hatches, and making sure engineers can get to the outdoor unit location saves time on the day.
- Sort permissions first. If you need freeholder consent, get in touch early so we can provide the technical details they'll ask for.
- Choose stock models. Popular units from major brands ship faster than special-order configurations.
The Short Version
A single wall-mounted split takes a day. Multi-room systems take 2-4 days. Ducted systems take 3-5 days. Commercial VRF takes weeks. The biggest variables are pipe run distance, wall construction, electrical requirements, and whether you need planning or leasehold consent.
If you want a proper timeline for your specific property, book a free site survey and we'll give you exact timescales before any commitment. We've been installing air conditioning across London since 2004, so we know what to expect from every type of building in this city.
Written by
Ali Elm
Ali is the Head of Operations at Be Cool Refrigeration with over a decade of hands-on experience in HVAC and commercial refrigeration. He oversees every installation, repair, and maintenance project, making sure the work meets the highest standards. Ali holds full F-Gas certification and has worked across residential, commercial, and industrial refrigeration systems throughout London and the South East. When he is not on site, he writes these guides to help business owners and homeowners understand their cooling systems better.