Air Conditioning Buying Guide:
Comparison, Reviews & FAQ

Air conditioners are available in different sizes and designs. The device that best fits your home depends on various factors. We will show you what you should consider when choosing your air cooler, how to choose the right size and which details play an important role when comparing air con units.

Functions and characteristics of different air conditioners

When the heat of the summer months makes staying at home a nuisance, many people consider buying an air conditioner. There is a wide range of air coolers available. The selection ranges from portable compact air conditioners, air coolers and simple fans to permanently installed air conditioners for apartments or houses. Therefore, the decision for a particular variant and model can become a challenge. First, your personal requirements are important. Depending on the type of unit, the equipment includes numerous additional functions, such as air cleaning, room air humidification or a heating function for the winter months.

In addition, the functioning differs depending on the device, which is why there is no simple answer to what the best model is. Certain factors such as your individual needs as well as the available budget are always decisive. To make your decision a little easier, we will give you a comprehensive insight into the advantages and disadvantages of different air conditioners and explain how they work.

Fans - simple but effective

Der Erfrischungssturm: Mit dem Klarstein Silent Storm Standventilator ist für das perfekte Raumklima gesorgt!

Product Review

Silent Storm Stand-Alone Fan

With 5 ventilation modes and 10 wind speed levels, the Silent Storm provides a refreshing breeze with low noise levels.

  • Especially quiet: with 32dB, it is as quiet as a whisper
  • Flexible: rheight-adjustable and tiltable rotor with connectible oscillation
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What we wouldn't give for a pleasant breeze a warm day. If the air in the office or at home seems to stand still again, fans can help. By moving their rotor blades, they create a pleasant flow of air. If placed in front of a window, they can also help to exchange air in a full room. Unlike mobile air conditioners or air coolers, however, they do not have a built-in cooling mechanism such as a water tank or cooling elements. The cooling effect is only provided by the airflow generated.


  • Saving space
  • Easy Installation
  • Cheaper than permanently installed devices
  • Mobile friendly


  • Limited range
  • No lowering of the indoor air temperature

Air cooler - compact air conditioner without hose

Das 4-in-1 Klimagerät Skyscraper Ice von Klarstein überragt optisch und leistungstechnisch seine Kollegen und bringt frische Luft in deine Räume.

Product Review

Skyscraper Ice 4-in-1 Air Cooler

The Skyscraper is a real all-rounder: it works like a fan and cools, humidifies and ionises the air at the same time.

  • Cooling provided by a 6 litre water tank
  • Air ionisation to eliminate odours and germs
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Portable air conditioners are available in different versions. Many consumers are looking for a unit without an exhaust hose and would also like to avoid using a cooling agent. A compact air cooler is an interesting alternative to a fan, mini air conditioner and split air conditioner unit. It does completely without a power-intensive cooling circuit requiring a cooling agent and compressor.

In this case, the reduction of the room temperature is achieved by the physical principle of evaporative cooling. The unit is based on the principle of a fan: The cooling of the air flow is achieved by means of the natural principle of water evaporation: The 3-in-1 air cooler draws in warm air at the rear of the unit and directs it through the evaporator. Thereby, the water extracts heat from it and the escaping airflow becomes colder. This will provide your body with the well-needed refreshment for any activity. The air is enriched with pleasant moisture, which provides relief especially on dry, hot days or with heating air in winter. The water tank needs to be refilled regularly. In addition to water, it is also possible to use cooling packs or ice cubes. Air coolers with integrated air filters are particularly practical for persons suffering from allergies.


  • Saving space
  • Easy Installation
  • Mobile Friendly
  • Low noise level
  • Humidification of the room air


  • No temperature reduction in the indoor air
  • Not recommended for regions with high humidity
  • Limited range

Portable air conditioning for individual use

Die Klarstein Pure Blizzard 3 2G Klimaanlage sorgt für klare, gekühlte Raumluft an heißen Sommertagen

Product Review

Pure Blizzard 3 2G portable air conditioning

The Pure Blizzard offers clear, cooled ambient air on hot summer days and ensures a pleasant room climate with fan and dehumidifier.

  • 3-in-1 device: aircon, dehumidification and ventilation
  • Discharge air with the exhaust hose: delivery includes window sealing
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This variant is also known under the name monoblock. It draws hot air in and conducts it through the integrated coolant circuit inside the device by means of a compressor. It is cooled and then returned to the room as a cool air stream. The warm exhaust air is then led to the outside through the exhaust hose.

Similar to a classic ventilation dryer, you can simply direct the hose out through a slightly open window. Usually, suitable assembly material is included in the delivery, allowing you to reliably attach and seal the hose on a window. Extensive construction work is therefore not necessary with these devices. This offers the benefit that you can simply transport a portable air cooler to another room and set it up if necessary.


  • Save Space
  • Easy installation on door or window
  • Cheaper than permanently installed devices
  • Effective room temperature reduction


  • Installation on window or door required
  • Higher power consumption during continuous operation
  • Not suitable for regions with low humidity

How does a split air conditioner work?

Mit der leistungsstarken und umweltschonenden Klarstein Windwaker Eco Split-Klimaanlage dank vieler Einstellungsmöglichkeiten jederzeit ein perfektes Raumklima

Product Review

Windwaker Smart Air Conditioner

the Windwaker Eco Split air conditioning system with energy efficiency classes A ++ / A +, an air flow of 610 m³ / h and five different operating modes makes it possible.

  • adjustable temperatures between 16 and 30 ° C
  • Energy efficiency class cooling mode: A ++ / heating mode: A +
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This variant consists of two devices, an indoor and an outdoor device. Inside, the indoor unit draws room air in, which is then filtered and cooled. The second device is installed outdoors and contains a cooling compressor. Both parts of the device are fixed and connected with a hose tube. A major advantage of this variant is the low-noise level, since the more noise-intensive compressor is installed outside. Most split air conditioning systems come with a reverse function. This enables the use as a heating device in the winter months. The installation must be carried out by an experienced professional.


  • Two-part operating principle = increased cooling capacity
  • Low noise level inside
  • Room temperature can be kept at a constant level
  • Mostly equipped with reverse function = can also be used as a heater


  • Installation by a specialist company required
  • Price is more expensive than most mobile devices
  • High electricity costs when used as heating

Comparison Table of Cooling Devices

How to calculate the cooling capacity of (mobile) air conditioning systems

When purchasing a new air conditioning system, cooling performance is an important factor. A comparison of different models shows that performance can vary greatly. The amount of thermal energy that the device dissipates per unit of time has an impact on the operating costs. In addition, it is important whether the selected device is optimal for the respective room size. If the unit is too small, the room will not be cooled adequately. An oversized choice, on the other hand, is also not recommended. Two units of measurement are important to determine the cooling performance: BTU and (kilo) watts. BTU stands for British Thermal Unit and denotes the cooling capacity (per hour) for air conditioning systems.

With this rule of thumb, you can determine the appropriate cooling capacity for your room size: calculate your room area in square meters times 60 watts (with good insulation and little sun exposure) to 100 watts (with little insulation and high sun exposure). Example:

20 m² x 100 W = 2000 W

(1000 W = 1 kW = 3412,14 BTU)

In a 20 square meter room with little insulation and high solar radiation, you will need a device with a cooling capacity of 2kW and around 6800BTU/h.

In addition to insulation and solar radiation, the number of people and technical devices in the room also influence the selection of the appropriate cooling capacity. Add about 250 watts for each additional person and the wattage for each electronic device in the room. You can find out the consumption of a device in the operating instructions or on the type label of the device.

Consequently, you will need more powerful devices to get efficient cooling for larger rooms. In smaller, sporadically used, rooms, you can use a mobile air conditioning system with an exhaust hose (there are no versions without a hose) . A permanently installed device is an ideal air conditioning option for the bedroom, but the costs are usually somewhat higher.

Air conditioning systems in comparison - find the right one for you

Fans Air Cooler Mobile Air Conditioning Split Air Conditioning
Cooling Type Thanks to its airflow, a fan offers a pleasant refreshment on hot summer days. It helps regulate the body temperature and gives us a cooling sensation, even if the room temperature itself is not reduced. The air cooler draws warm air in, evaporates water and cools the air flowing through it. This ensures that our body is pleasantly cooled, even if the room temperature itself is not significantly reduced. The mobile air conditioning system ensures a pleasant cooling of the room. The warm summer air is drawn in and cooled down by a compressor, like in a refrigerator. The resulting warm air is led outside through an exhaust hose. The split air conditioning system cools the room air using a cooling agent. The warm air that is absorbed by the indoor unit vaporises the agent and leads it to the outdoor unit. There, the heat is dissipated, the coolant liquefies again and is returned to the inside. This cycle is repeated until the desired room temperature is reached.
Weight The weight of fans (depending on the model) is usually between 1-8kg. The weight of air coolers is between 6-10kg. The weight of monoblock systems is between 10-30kg. The weight for the outdoor and indoor unit together is usually around 50kg. The indoor unit weighs approx. 10kg, the outdoor unit approx. 40kg.
Cooling Capacity No direct reduction in room temperature No direct reduction in room temperature The cooling capacity of mobile air conditioning systems is usually between 2-3kW. This allows the cooling of a room with a volume of 80-120m³. The mobile air conditioning system is therefore more suitable for small rooms and rather for sporadic use. The split air conditioning units usually have a higher cooling capacity than mobile air conditioning units or air coolers. Therefore, they are particularly suitable for larger rooms. The power range starts at 2.5kW and ranges to devices with 12kW.
Power consumption and energy efficiency Of all the devices listed here, fans usually have the lowest power consumption. Compared to monoblock and split air conditioning systems, an air cooler performs better in terms of electricity costs. The power consumption of these devices can even be higher than with a modern split air conditioning system. Therefore, monoblock devices are particularly well suited for sporadic use. IGood split air conditioners have a lower power consumption than mobile air conditioners. It also depends on the energy efficiency class. Classes A to A +++ are recommended here.
Sound Volume Level On average, fans are quieter than other air con units. Air coolers work without a compressor and therefore cool the room air much more quietly than the other air conditioning systems. The mobile devices reach a volume between 60-65dB and are therefore the loudest in comparison to other cooling devices. Split air conditioners are usually quieter than e.g. mobile air conditioners. The indoor unit reaches a sound pressure level of up to 50dB. The sound pressure level on the outdoor unit, however, can be up to 60dB.

Frequently Asked Questions

The correct positioning has a significant impact on cooling performance and cost efficiency. Wherever possible, you should not place portable devices too close to walls, and there should be no heat sources such as lamps nearby. Regardless of the option chosen, a power connection should always be within reach. If you are installing a split system, you should definitely take this point into account when planning. Otherwise, it may be necessary for an electrician to run a new cable for an additional connection.

This variant allows the connection of several indoor units to the outdoor unit. Depending on the version, up to 5 indoor units can be connected. Therefore, you can cool several rooms or entire floors with this variant.

We can absolutely advise against this. You should definitely leave this task to an experienced specialist company. Specialist know-how is indispensable for the planning and assembly of these complex systems. Furthermore, no specialist company is liable for possible errors and damage that may occur during self-installation. A leaking coolant from an improper installation, can have serious consequences for health and the environment.

For larger systems with a fill volume of around 2.5 to 3kg, maintenance is recommended once a year; for smaller units, a maintenance interval of 2 to 3 years is usually sufficient. Thereby, the filter can be checked and replaced, if necessary. The maintenance is usually carried out by air conditioning, heating and sanitary specialists. The refrigeration technology of complex systems can also be checked regularly by an electrician.

There can be various reasons for an insufficient cooling capacity. For example, an insufficient amount of coolant or a defective or dirty filter might be the reason. If in doubt, you should contact a specialist company.

Basically, you should pay attention on the relationship to the environment in relation to relative humidity and temperature. It is advisable not to cool the respective room by more than 6 degrees compared to the outside temperature. This is advisable in order to avoid colds and circulatory problems due to an excessive temperature difference. If the humidity is too low, it can dry out the mucous membranes and thus irritate the respiratory tract. If it is too high, however, it can have a negative effect on the thermoregulation of the people in the room. A humidity of around 50 to 60 percent is ideal.

In the air conditioning test of the Stiftung Warentest, it was pointed out that the effects on climate depend on the choice of the cooling agent. Nowadays, legislators are ensuring that modern systems have to meet high requirements for approval.

Yes. Many companies offer special disinfection sprays with which you can disinfect your systems and thus prevent the formation of germs and fungi.

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