Air Conditioner Installation - What You Need to Know

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An air conditioner is only as good as its installation. Two completely identical units, one installed professionally according to the manufacturer's instructions and the other "by a neighbour for half the price", can in practice differ in cooling efficiency by as much as 20-30 %, without anything looking obviously wrong at first glance. The problem only shows up a year or two later, when refrigerant slowly leaks through a poorly sealed joint, the compressor becomes overloaded, and a unit that should have lasted 12-15 years is on its last legs after five. In this article we break down what installing an air conditioner actually involves, what most affects its price and complexity, what to look out for when choosing an installation company, and where people most often go wrong.

Why installation matters just as much as the unit itself

A split air conditioner consists of an indoor unit (the one you see on the wall in the room) and an outdoor unit (the compressor unit mounted on the façade, balcony, or roof). Between them run copper refrigerant piping with refrigerant, a condensate drain, and electrical cables. The product itself - the compressor, heat exchangers, electronics - is practically always fine straight from the factory; quality control at reputable brands is thorough. The weak link in the chain is almost always the installation: the quality of the pipe joints, how thoroughly the system is vacuum-evacuated, correctly sized refrigerant, and whether the outdoor unit is positioned with enough space for air exchange.

A leaking pipe joint doesn't show up right away. Refrigerant leaks slowly, and the unit initially cools almost normally, just a bit slower. Only once the refrigerant amount drops below a critical threshold does the compressor start operating in an unsuitable regime, noise increases, and eventually the compressor fails - the most expensive part in the whole unit. That's exactly why it's worth paying as much attention to choosing an installation company and monitoring the installation process as to choosing the air conditioner model itself.

How split air conditioner installation proceeds step by step

Most installations of a wall-mounted split air conditioner in a flat or family house follow the same basic procedure. The order of steps may vary slightly by company, but the content is always the same phases.

Step six - vacuum evacuation and the pressure test - is the most important step, and also the one most often skipped in "cheap" installations. The vacuum pump must run long enough (typically at least 20-30 minutes after reaching the required vacuum) to remove all moisture and air from the system. If this step is rushed in a couple of minutes or skipped entirely, moisture remains in the system, which over time causes corrosion inside the heat exchangers and freezing of the expansion valve. Ask the installation company directly how long the vacuum evacuation took and whether you can get a report, or at least a photo of the gauge.

What most affects the complexity and price of installation

In practice, the installation price consists of a base rate plus several surcharges depending on the specific situation in the flat or house. The typical price for a standard wall-mounted split installation - indoor unit within 3 metres of the outdoor one, brick or concrete wall, ground floor or an easily accessible upper floor - ranges from €150 to €250. On top of this come surcharges depending on the specific circumstances:

Extending the refrigerant piping beyond the standard distance - typically €15 to €25 for each additional running metre of copper piping including insulation and wiring.
Core drilling through a thicker wall (solid brick, concrete, a multi-layer façade with an insulation system) - a surcharge of approximately €30 to €50 compared to drilling through an ordinary partition.
A separate electrical circuit and breaker for more powerful units, if the flat lacks a suitable socket or wiring - typically an extra €50 to €100.
Work at height - when the outdoor unit cannot be mounted from a ladder and a lift platform or rope-access technique is needed (high-rise flats, difficult façade access) - here the surcharge can climb to €50 to €150, in extreme cases even more, depending on whether special equipment needs to be hired.

In reality, the resulting typical price for installing most domestic split air conditioners ranges from €150 to approximately €450. For more complicated installations (several indoor units on one outdoor unit, multi-split systems, very long pipe runs), the price can be even higher - here it's always better to ask for a specific quote after an on-site survey, not an estimate over the phone.

Who is allowed to install an air conditioner, and what to ask a company

Installing and servicing equipment containing fluorinated greenhouse gases (refrigerants such as R32, R410A, and similar, commonly used in domestic air conditioners) is subject to European F-gas legislation. In practice this means that work involving handling refrigerant - mainly connecting and vacuum-evacuating the circuit, topping up refrigerant, and checking tightness - should be carried out by a technician holding the appropriate professional certification. When booking an installation, it's entirely normal and legitimate to ask a company whether their technician holds such a certification - a reputable company will be able to answer without hesitation, or show you the certificate directly.

Besides professional qualification, it's worth checking a few practical things with a company before booking:

Whether the quote includes materials (piping, insulation, brackets, extra refrigerant) or just labour - a "tempting" low price often ends up higher once materials are billed separately.
What warranty applies to the installation (not just the product itself from the manufacturer) and exactly what this warranty covers.
Whether the company hands over a tightness test certificate after installation - for some larger or commercial systems this documentation is even a legal requirement, but even for an ordinary domestic air conditioner it's a sign of a professional approach.
How long the company has been operating and whether it has references - installing an air conditioner is a one-off investment for 10-15 years ahead, so it's worth vetting the company just as thoroughly as the product itself.

Positioning the outdoor unit - what not to forget

The outdoor unit needs free space for air intake and exhaust, otherwise its output and efficiency will noticeably worsen regardless of how good the model you bought is. Common manufacturer recommendations for free space around the unit look roughly like this: at least 30 cm of free space on the sides, a minimum of 60 cm of space in front of the unit (in the direction of air discharge), and at least 15-30 cm clearance from the house wall at the back. A unit placed tightly into a corner, between two walls, or under a low canopy without air circulation will work with noticeably worse efficiency in summer, because it draws in its own heated exhaust air.

The distance from windows also matters - it's best to position the outdoor unit at least a metre to the side of the nearest openable window, so that warm exhaust air doesn't flow directly indoors when ventilating. Typical outdoor unit noise at medium load is around 45 to 55 decibels (similar to a quiet conversation), which is why many municipalities, in neighbour disputes, recommend or directly require a certain distance from the boundary of a neighbouring property - specific rules vary from municipality to municipality, so if installing near a property boundary, it's worth checking the local regulation in advance, not after a complaint arrives.

How long installation takes and what to prepare in advance

Under standard conditions, a typical installation of one wall-mounted split air conditioner in a flat or family house takes approximately 4 to 8 hours, so it can usually be handled within a single working day. For a more complicated pipe route, core drilling through a thicker wall, or installing several indoor units on one outdoor unit (multi-split), the time can extend to two days.

Before the installation company arrives, it's worth thinking through a few things:

Pipe route - the shortest and most direct path between the indoor and outdoor unit means less material, fewer surcharges, and better efficiency. Manufacturers of ordinary domestic units typically state a maximum recommended pipe length of 15 to 20 metres and a maximum height difference between units of up to 10 metres - beyond this range, the unit's output and efficiency start to drop, or additional refrigerant top-up may be needed.
Access to the outdoor unit's installation site - if it's a higher floor without a balcony, ask the company in advance whether a lift platform will be needed and who will provide it, so you're not caught off guard on installation day.
Condensate drainage - in summer an air conditioner can produce several litres of condensed water a day; you need to think through where this water will drain (a connection to the waste system, a downpipe on the façade, or a condensate pump if the unit isn't above a drain).
Free access to the room and to the façade throughout the whole installation day - the company will need access both inside and outside, so plan for this.

The most common installation mistakes

Some mistakes can be spotted even by a layperson right after installation, others only show up months later. Here's an overview of the most common ones:

The common denominator of most of these mistakes is trying to save time on steps that aren't visible from the outside - vacuum evacuation, condensate slope, thorough flaring of pipe joints. This is exactly why it doesn't pay to choose an installation company based on price alone; a difference of €50-100 between quotes can, in the end, be the difference between a unit that lasts 15 years without issues and one that suffers a compressor fault after two years due to a refrigerant leak.

Recommended models for installation

When choosing a specific model for installation, it's worth selecting output based on the room's size - lower output is enough for a small room, and an unnecessarily oversized unit in a small room often also switches on and off in short cycles, which does it no favours. Here are three proven Vaillant ClimaVAIR pro models that cover the typical range of rooms from a smaller bedroom to a larger living room:

VAIB1-025WN outdoor and indoor unit with remote control - the smallest model in the series, suitable for smaller rooms and bedrooms up to approx. 25-30 m². Lower cooling output also means lower installation cost in a reasonably sized space, making it an ideal first step if you're only air-conditioning one or two rooms. Price from €527.00.

VAIB1-035WN outdoor and indoor unit with remote control - a mid-power step, a common choice for a medium-sized living room or an open living space connected to a kitchen. When installing this output class, it's especially worth ensuring the pipe run is correctly sized, so the unit delivers its stated output even on the hottest days. Price from €561.00.

VAIB1-050WN outdoor and indoor unit with remote control - the most powerful of the three, suitable for larger rooms or spaces with high heat gains (large glazed areas, south-facing orientation). At this output class, the outdoor unit tends to be somewhat larger and heavier, which needs to be taken into account when choosing the mounting bracket and its anchoring to the façade. Price from €833.00.

Installation in a flat vs. a family house - what's the difference

In a family house, installation is generally simpler - the owner decides on the outdoor unit's placement themselves, the façade is usually more easily accessible from a ladder or directly from the ground, and no one else's consent is needed. The only complication might be a longer distance between the room you want to cool and a suitable spot on the façade (for example an upstairs room facing a side where you don't want the outdoor unit visible from the street) - this lengthens the pipe run, and with it, the price.

In a flat, especially in an apartment building with a shared façade, several extra steps are added. The first is the already-mentioned consent of the owners' association or property manager - in many buildings, placing an air conditioner on the façade is regulated by house rules, and without consent the manager may require removal of the unit even after some time. The second is the piping passing through the perimeter structure, which in apartment buildings is often thicker and sometimes insulated with an external thermal insulation system - in that case, core drilling needs to be done carefully so as not to damage the insulation around the opening and create a thermal bridge. The third difference is floor level - upper floors without a balcony or loggia often require work at height, which we covered in the pricing section above.

For a flat in an apartment building, it's also worth thinking through the aesthetic side in advance - exactly where the outdoor unit will be visible from the street or from neighbours, and whether there's a possibility to place it, for example, on the roof of shared spaces instead of the façade (in some buildings this is common practice when handling air conditioning collectively for several flats at once). Such a solution requires longer piping and therefore a higher installation price, but the result is visually cleaner and often quieter for the flat owner too, since the unit isn't right outside the window.

After installation - what to check and what to ask

Right after the installation is finished, it's worth going through a few things together with the technician while they're still on site. Check that the indoor unit doesn't make any unusual noises during operation (bubbling, clicking, whistling), that water actually drains from the condensate outlet during a test run, and that the outdoor unit is firmly anchored with no visible wobbling. Ask for a document confirming the installation, stating the type and amount of refrigerant, the date, and the technician's signature - you'll need this document for any future claim as well as for regular servicing.

The warranty on the equipment itself is the manufacturer's responsibility; the warranty on the installation (i.e. the work) is the installation company's responsibility - these two things are sometimes confused, but they're separate obligations of separate parties. If a refrigerant leak caused by a poorly made joint appears within a year, that's an installation claim against the company that carried out the work, not against the unit's manufacturer.

Frequently asked questions

Can an air conditioner be installed in winter?

Yes, installation itself isn't tied to the season - a technician can mount, connect, vacuum-evacuate, and test the unit even in winter. The only limitation is that the final test of cooling output at low outdoor temperatures may not be fully accurate, since most units have a minimum operating temperature range specified for cooling mode. If you also plan to use the air conditioner for heating during the transitional season, this can be verified immediately; the cooling function is only reliably tested once the weather warms up.

Do I need a building permit to install an air conditioner?

An ordinary split air conditioner installation in a flat or family house generally doesn't require a building permit or a notification, since it doesn't involve any work on load-bearing structures. An exception can be apartment buildings with shared façades, where some owners' associations or property management companies require consent for placing the outdoor unit on the façade - this is worth checking in advance directly with the building manager, not on installation day.

Can I install an air conditioner myself if I'm handy?

The mechanical part - mounting the indoor unit, laying the piping, securing the outdoor unit - can be managed by a handy DIYer. The problem is the refrigerant part: vacuum-evacuating the circuit, checking tightness, and any refrigerant top-up require specialised tools (a vacuum pump, a gauge set) as well as experience working with F-gases. Without this step, exactly the risk we described above arises - a slow refrigerant leak and compressor damage within the first years of operation.

How long does a correctly installed air conditioner last?

With quality installation and regular maintenance (filter cleaning, an inspection once a year or two), the typical service life of a domestic split air conditioner is around 12 to 15 years. Poor installation can significantly shorten this lifespan, especially if a slow refrigerant leak occurs and goes unnoticed for a long time.

What if the outdoor unit can't go on the façade facing the neighbour?

In that case it's best to look for an alternative location - a balcony, a roof with its own stand, or a wall facing a different direction. If the façade facing the neighbour is the only real option, it's worth discussing the placement with the neighbour in advance and choosing as quiet a model as possible, or adding a noise barrier. This avoids potential disputes after installation, which are much harder to resolve than beforehand.

Is it worth handling several rooms at once during installation?

If you already know you want to air-condition two or more rooms, it's worth handling this at once - either as a multi-split system (one outdoor unit, several indoor units), or at least by planning the cable and pipe routes so they can be easily extended later. Installing a second unit a year later often ends up more expensive than doing it together with the first, since the technician has already been on site with the equipment, and part of the work (for example redoing the electrical wiring) can be done at the same time.

Do you have a question about this topic?

Can't decide, or dealing with a specific situation in your household? Write to us - we're happy to help.