Frequently Asked Questions About Air Conditioners and Dehumidifiers

We are still preparing products.

But you can look at other categories.

Air conditioners and dehumidifiers are among the products for which we receive the most inquiries at atria.sk, as customers are often unsure of exactly what they need. Below we have listed the questions that we receive most frequently by phone, email, and in product discussions, and we answer them as we would for a neighbor - without unnecessary sales fluff, but also without avoiding unpleasant facts (for example, that an air conditioner in an old panel building without insulation will have different parameters than in a new building).

What air conditioner capacity do you actually need?

This is by far the most common question and also the one where the most mistakes are made - usually in the direction of underdimensioning. A customer might say, "I have a room of 20 m², I'll buy a smaller unit and save money," and in the summer then finds out that the air conditioner runs non-stop at full capacity and still cannot cool the room to the desired temperature.

Approximate calculation that actually works

In practice, a simple rule is most often used: for a standard insulated room in an apartment building, calculate a cooling capacity of approximately 100 W per square meter of floor area with a standard ceiling height of up to 2.7 m. In a new building with good insulation and triple glazing, you can go slightly lower. On the other hand, for a room with large south or west-facing glazed areas, a roof room under a metal roof, or a space where computers or kitchen appliances generate heat, you should add a 15-30 % margin to the basic calculation.

In practice, it looks like this: a unit with a cooling capacity of around 2.5 kW reliably covers a room up to about 25 m², a unit around 3.5 kW can handle a room up to about 35 m², and a more powerful 5.0 kW variant is suitable for a larger living room or a combined living space up to about 50 m². These are approximate values for a typical Slovak apartment or family house, not laboratory numbers - for a specific project (such as a glazed office or a basement room), we always recommend consulting directly with an installation company that can carry out an inspection.

Recommended models according to power ranges (Vaillant climaVAIR pro, single split - outdoor and indoor unit with remote control in the package):

VAIB1-025WN outdoor and indoor unit with remote control - a smaller capacity variant suitable for a standard bedroom, children's room, or office up to about 25 m². A complete single-split package including a remote control, nothing else needs to be purchased except installation. Price from 527.00 EUR.

VAIB1-035WN outdoor and indoor unit with remote control - a medium capacity variant, the most universal choice for a standard living room or larger room up to about 35 m². The most frequently sold capacity in this range precisely due to the price-to-universality ratio. Price from 561.00 EUR.

VAIB1-050WN outdoor and indoor unit with remote control - the most powerful variant in the range, suitable for a combined living space or larger room up to about 50 m², or where there is increased thermal load (glazing, southern orientation). Price from 833.00 EUR.

Air conditioner or dehumidifier - what is the difference and when is the cheaper solution sufficient

The second most common question is approximately as follows: "Will a dehumidifier be enough for me, or do I need an air conditioner?" The answer depends on what your actual problem is - heat or humidity.

An air conditioner primarily cools the air (it removes heat and transfers it outside via the outdoor unit), it only reduces humidity as a by-product of condensation on the evaporator. A dehumidifier, on the other hand, does not significantly cool or heat the air. Its only function is to reduce the relative humidity of the air - in summer and winter, regardless of the temperature. If you are therefore struggling with mold in the bathroom, fogged windows in the bedroom during winter, or need to dry a laundry room without a window, a dehumidifier is a cheaper and more energy-efficient solution. If your problem is high room temperature during the summer, you need an air conditioner - a dehumidifier will not solve the heat issue.

A common mistake we encounter in discussions: a customer buys a dehumidifier in the hope that it will "at least cool a bit" an overheated basement room in the summer. In reality, a dehumidifier slightly heats the air (the compressor and motor produce heat that is returned to the room), so in a hot room it will worsen the situation rather than improve it.

When is the combination of both beneficial

In practice, the combination works well in homes with basements or in newly built houses immediately after completion, where the structure still contains a lot of residual moisture - air conditioning handles summer temperatures in living areas, while a small dehumidifier running in the basement or laundry room protects against mold independently of the season.

How much will air conditioning cost me to operate

This is a question customers often ask after purchase, when a higher electricity bill arrives - yet an approximate calculation is not complicated. Modern inverter air conditioners (and all units we sell are inverter type) have a cooling coefficient of performance (EER) typically ranging from 3 to 4, meaning that for 1 kW of electrical input, they can remove 3 to 4 kW of heat from the room. Cooling a room with a 2.5 kW unit practically means an electrical input of approximately 0.6-0.8 kW when running at full capacity - however, with inverter regulation, the unit usually runs at partial capacity most of the time, as it only maintains the achieved temperature, so the actual average consumption during the day is significantly lower than when running at maximum.

Practical example: if a 2.5 kW unit runs on a hot summer day for about 6 hours at an average input of 0.4 kW (a combination of full-power starts and maintenance mode), the daily consumption is approximately 2.4 kWh. At standard electricity prices, this amounts to single-digit euros per day of intensive operation, not tens. For a larger 5.0 kW unit and a larger room, the numbers increase proportionally, but the principle remains the same - inverter regulation is key and is the reason why units without it are almost never sold today.

What increases consumption the most in practice

From specific cases we handle through discussions and service, the most common reasons for unnecessarily high consumption are: a target temperature set too low (a 5 °C difference from the outside temperature is completely sufficient and noticeable, each additional degree increases consumption disproportionately), open windows or doors during cooling, a dirty air filter (which restricts airflow and forces the unit to work harder), and an undersized capacity relative to the room area - as mentioned in the section above on capacity.

Installation and common faults - what to prepare for

Installation of a split air conditioner (external + internal unit connected by refrigerant piping) is not a do-it-yourself task - it requires professional handling of refrigerant, vacuuming the circuit, and electrical wiring, which should be done by a certified installer. The standard installation cost depends on the length of the piping route and the complexity of placing the external unit (balcony, façade, roof), so we always recommend having it evaluated by a specific installation company in your region on-site.

As for common faults, in the vast majority of cases we handle through customer support, it usually comes down to one of several typical situations - and most of them can be checked by you before calling a service.

Frozen internal unit

If frost or ice appears on the internal unit or on the cooling piping, the most common cause is insufficient airflow (dirty filter, unit covered by furniture or curtains) or operation at too low an outside temperature in cooling mode, which the unit is not designed for. In such a case, turn off the unit, let it fully defrost (do not scrape the ice forcefully), and check the filter and free space around the unit.

External unit is noisy or vibrating

Increased noise or vibration is often caused by improper mounting of the external unit bracket on the façade, missing rubber dampers, or a dirty fan and condenser (e.g., dust, leaves, construction dust from the surrounding area). Regular cleaning of the external unit once a year, ideally in spring before the season, prevents most of these issues.

Dehumidifiers - most common questions from practice

With dehumidifiers, we mainly address two things: which size (capacity) model to choose and exactly where to place it in the apartment.

What humidity level is acceptable in the apartment

For a standard living room, a relative humidity of 40-60 % is recommended. Below this threshold, the air becomes uncomfortably dry (irritated mucous membranes, static electricity), while above 60 % relative humidity significantly increases the risk of condensation on cold areas (room corners, window sills, corners behind furniture near the perimeter wall), and thus the risk of mold. A cheap hygrometer is a good first investment before buying a dehumidifier - it will show you whether the problem actually exists and how severe it is.

Where to place the dehumidifier

The dehumidifier should be placed freely, at least 15-20 cm away from the wall and furniture, to ensure sufficient space for air intake and exhaust, and in the room with the biggest problem (bathroom without a window, laundry room, basement, newly built house right after completion). Keep the doors to other rooms slightly open during operation if you want to extend the effect beyond one room - air naturally circulates throughout the apartment.

Comparison of operating costs by power range

Since the price of the unit is only one part of the decision, let's also look at how the initial investment differs across the presented range - with the same technology (inverter, same brand and range), the price difference is mainly due to the size of the compressor and heat exchangers, i.e., real capacity, not an unnecessary premium for "higher class".

As we can see, the difference between the 2.5 kW and 3.5 kW variant is quite small (approx. 34 EUR), while the jump to the 5.0 kW variant is more significant - this corresponds to the actual increase in performance and component size. Practical recommendation: if you are hesitating between two adjacent power levels and your room is on the borderline, it is worth going for the more powerful variant - the additional cost is usually smaller than the extra expenses and stress caused by an underdimensioned unit that cannot cope with cooling on the hottest days.

Air conditioning for heating as well - does it make sense in Slovakia

Most modern split air conditioners, including the series presented, also operate in the mode of an air-to-air heat pump, meaning they can heat a room as well as cool it. For many customers, this is a pleasant bonus especially during transitional periods (spring, autumn), when it is worth using it for heating without having to start the entire heating system. However, you should keep in mind that the efficiency of heating via air conditioning significantly decreases at low outdoor temperatures (usually below approximately -5 to -10 °C depending on the specific model), so in our climatic conditions, an air conditioner with a heating function is recommended as a supplementary, not a main, source of heat in winter months.

The most common myths about air conditioners that we encounter

Along with specific technical questions, customers often repeat statements they heard from a neighbor, in a discussion forum, or simply remembered from the past, but which are no longer valid or were never entirely accurate. A few of the most widespread ones are worth putting into perspective.

Myth: Air conditioners cause colds and flu

A cold draft directed directly at the body for a longer period of time can indeed cause discomfort, especially if the difference between the outside and inside temperature is extreme or if the air stream is directed directly at the neck or back while sitting. However, the cause is not the air conditioner itself, but the incorrect setting of the louvers and an overly aggressive target temperature. The recommended temperature difference from the outside is approximately 5 °C, and the louvers should be directed diagonally upwards or into the space, not directly at the place where you sit or sleep.

Myth: The more expensive the air conditioner, the better it is automatically

Within a single series (as we have shown in the comparison above), the price largely reflects the actual performance - a larger compressor, larger heat exchangers, and a more powerful fan. A higher price therefore does not mean a "better" unit in an absolute sense, it means higher performance for a larger space. Buying an overdimensioned unit for a small room makes no sense - apart from the unnecessarily higher price, it can also lead to an unpleasant effect of rapid cooling and reheating (so-called cycling), which reduces comfort and the lifespan of the compressor.

Myth: Air conditioners dry the air so much that it harms health

A slight drop in humidity during cooling does indeed occur (condensation on the evaporator), but in a normal living room with proper temperature settings, this is usually not so pronounced as to pose a health problem. For more sensitive individuals or during very long operation, the effect can be compensated by placing plants in the room, a bowl of water on a radiator outside the cooling season, or in extreme cases, by using a humidifier - but in practice, very few people do this, as the real impact is negligible.

Myth: A dehumidifier needs to be turned on only when condensation is visible on the windows

Condensation on the glass is the last stage, when the air humidity is already significantly increased. Before that, humidity often accumulates invisibly in less ventilated corners, behind cabinets near the perimeter wall, or in the attic - it is precisely there that you will later find mold without having noticed the fogged window. Regular measurement with a hygrometer and preventive activation of the dehumidifier before visible symptoms appear is a much more reliable approach than waiting for fogged glass.

How to decide if you are still hesitating

If after reading all of the above you are still unsure, we recommend proceeding in three steps. First, accurately measure the area of the room and note the orientation of the windows, the size of the glazing, and any heat sources (electronics, kitchen stove) - these data will be needed when selecting the power and when consulting with the installation company. Second, decide whether your primary problem is temperature (you need an air conditioner) or humidity (you need a dehumidifier, or both devices independently of each other). Third, when hesitating between two adjacent power variants, go for the more powerful one - the price difference is usually smaller than you might expect, while an underdimensioned unit will cause problems throughout the entire season.

In the case of larger or atypical spaces (office open spaces, shops, industrial halls), it is always most reliable to have an on-site inspection done directly by the installation company - they can take into account factors that cannot be read from a tabular calculation, such as air flow in the space, the number of people who usually stay in the room, or the heat losses of the specific building.

Frequently asked questions

Does the air conditioner need to be turned on all day to work efficiently?

No, quite the opposite. An inverter air conditioner is most efficient when it maintains the already achieved temperature through mild power regulation, not when it repeatedly starts from a switched-off state at full power. If you are at home most of the day, it is worth leaving it running at a reasonable temperature (e.g. 25 °C) continuously, rather than turning it off and on.

Can an air conditioner be installed in a rented apartment without any changes to the facade?

Changes to the facade (drilling a hole in the wall for the pipe, securing the console of the outdoor unit) are practically always necessary with a classic split system, so in a rental agreement, the consent of the property owner is necessary, or even the owners' association in the case of an apartment building. An alternative without changes to the facade is a mobile air conditioner with a hose vented through the window, but it has lower efficiency and higher noise compared to a split unit.

How often should the air conditioner filter be cleaned?

During the season (June to September for regular use), we recommend visually checking and cleaning the filter every 2-4 weeks, more frequently in case of intensive use or in a dusty environment. A neglected filter is the most common cause of unnecessarily high consumption and reduced cooling performance.

Can I install the air conditioner myself if I have experience with home repairs?

We do not recommend it. Installation of a split air conditioner requires working with refrigerant, vacuuming the circuit, and professional electrical installation - in addition to the safety risk, DIY installation usually also means losing the warranty on the unit. Always leave the installation to a certified installation company.

Is one dehumidifier enough for the whole apartment?

It depends on the layout and where the problem is the greatest. In an apartment with an open space (kitchen connected to the living room) and open doors to other rooms, one medium-performance dehumidifier may be sufficient for the entire apartment. In the case of multiple enclosed rooms with their own source of humidity (bathroom and laundry room separately), it is more effective to address them separately, or to move the dehumidifier between rooms over time.

Is it worth waiting for a discount outside the season, or should I buy the air conditioner right in the summer?

From the perspective of the availability of installation companies, purchasing outside the main summer season (autumn, winter, early spring) is usually more advantageous not necessarily in terms of product price, but in terms of the speed and availability of the installation appointment - in July and August, installation capacities are usually fully booked and waiting times can extend to weeks.

Do you have a question on this topic?

Having trouble making a decision or dealing with a specific situation in your home? Write to us - we'll be happy to help.