The cooling capacity of an air conditioner indicates how much heat the device can remove from a room, expressed in kilowatts (kW). The electrical power indicates how much energy the device consumes to do this. The main difference: an air conditioner always delivers more cooling capacity than it consumes in electricity, thanks to heat pump operation. The ratio between these two numbers tells you how efficiently an air conditioner operates. In this article, we answer the most frequently asked questions about cooling capacity, electrical power, and how to make the right choice for your situation.

How is cooling capacity measured in an air conditioner?

The cooling capacity of an air conditioner is measured in kilowatts (kW) and indicates how much thermal energy the device can extract from a room per hour. An air conditioner with a cooling capacity of 3,5 kW can remove 3,5 kilowatt-hours of heat per hour. The higher this number, the greater the cooling capacity of the device.

The measurement is performed under standardized test conditions so that you can compare devices fairly. Manufacturers typically measure cooling capacity at an outdoor temperature of 35 degrees Celsius and an indoor temperature of 27 degrees. In practice, the actual cooling capacity may vary slightly depending on the conditions in and around your home.

In addition to kilowatts, you sometimes see the unit BTU (British Thermal Unit) used, particularly in older or American specifications. One kilowatt is equivalent to approximately 3.412 BTU per hour. For most European purchases in 2026, kW is the standard unit to look out for.

What does the electrical output say about the energy consumption of an air conditioner?

The electrical power of an air conditioner, also expressed in kilowatts (kW), indicates how much power the device consumes to operate. This is the power you see on your energy bill. An air conditioner with an electrical power of 1,2 kW consumes 1,2 kilowatt-hours of electricity when running for one hour.

Electrical power is therefore not the same as cooling capacity. It is the system's input, whereas cooling capacity is the output. Thanks to the heat pump operation of an air conditioner, the output is always greater than the input: the device moves heat instead of generating it, which makes it significantly more efficient than, for example, an electric heater.

In modern inverter air conditioning systems, the electrical output varies constantly. The compressor adjusts its speed based on the needs of the room. This means that the stated electrical output is a maximum value and that the device often operates more efficiently in practice. If you want to know how efficiently a specific model operates, use the air conditioning selection guide to compare models.

What is the ratio between cooling capacity and electrical power?

The ratio between cooling capacity and electrical power is called the COP (Coefficient of Performance) for heating, or the EER (Energy Efficiency Ratio) for cooling. An EER of 3,5 means that the air conditioner delivers 3,5 kilowatts of cooling capacity for every kilowatt of electricity. The higher this ratio, the more efficient the device.

A modern split air conditioner typically has an EER between 3 and 5. That sounds abstract, but in concrete terms, it means that for every euro spent on electricity, you get three to five times more cooling capacity than with an electric fan or ventilator that doesn't actually cool the air.

In European energy labels, seasonal efficiency is measured via the SEER (Seasonal Energy Efficiency Ratio). This figure takes into account fluctuating outdoor temperatures over an entire season, providing a more realistic picture of annual consumption than a single EER measurement.

Why is high cooling capacity not always better?

Excessive cooling capacity for the room causes the air conditioner to reach the set temperature too quickly and then switch off. This short on-and-off cycling, also known as short cycling, is inefficient and causes the compressor to wear out faster. Furthermore, the air cools down too quickly without sufficient moisture removal, resulting in a clammy feeling.

An air conditioner works most efficiently when it runs at a lower speed for extended periods. That is exactly what an inverter system does: it continuously modulates its power. However, even an inverter system has a lower limit. If the room is much too small for the selected power output, even the lowest setting may be too much.

In addition, a larger device entails higher purchase costs without offering any benefit in a small space. Choosing an appropriate cooling capacity is therefore a matter of balance: enough to cool the room effectively, but not so much that the system cannot do its job properly.

How do you choose the right proportions for your space?

As a rule of thumb, for a well-insulated room, you should account for approximately 80 to 100 watts of cooling capacity per square meter. A 30 m² living room would then require an air conditioner with a cooling capacity of roughly 2,4 to 3 kW. However, this is a starting point, not a fixed formula.

Several factors influence how much cooling capacity you actually need:

Insulation quality: Poorly insulated rooms heat up faster and require more cooling capacity.
Sun exposure: A south-facing room with large windows requires more cooling capacity than a north-facing room.
Ceiling height: A higher ceiling height means more air volume to cool.
Heat sources: Appliances, people, and cooking activities produce extra heat that your air conditioner must compensate for.
Climate: In regions with prolonged heatwaves, as is becoming increasingly common in the Netherlands, it may be sensible to allow for a slightly larger margin.

If in doubt, use a pricing tool for a targeted estimate based on your specific situation, so that you do not choose too much or too little cooling capacity.

What power ratings are listed on an air conditioner's energy label?

The European energy label of an air conditioner lists several power ratings. The most important are the nominal cooling capacity (in kW), the nominal electrical power during cooling (in kW), and the SEER value, which indicates the seasonal efficiency during cooling. For air conditioning systems with a heating function, the heating capacity and SCOP are also listed.

In 2026, the energy label ranges from class A to G, with A representing the most efficient appliances. A higher energy class means a better ratio between cooling capacity and electricity consumption over the entire season. For long-term use, it pays to choose an appliance in class A or B, even though the purchase price is slightly higher.

In addition to the SEER, the label also lists the annual energy consumption in kilowatt-hours, calculated based on a standard usage profile. This figure makes it easy to calculate the expected annual electricity costs and directly compare different models.

How De Betonboorder helps with the installation of your air conditioner

Choosing an air conditioner with the right cooling capacity is step one. Step two is installation, and that often involves drilling into concrete. The indoor and outdoor units of a split air conditioner must be connected via a penetration through the facade or wall, which in many homes is made of concrete or stone. This requires professional and precise work.

We help you with that in a concrete way:

Precision drilling through concrete, stone, and reinforced concrete for the passage of air conditioning pipes
Work dust-free and neatly, so that the workplace is left tidy afterwards
National network of professionals, in many cases available within two days
Suitable for private individuals, SMEs, and contractors

Do you want to know how much it costs to drill a through-hole for your air conditioning system or how soon we can come? Contact us and we respond within 24 hours.

What is the difference between cooling capacity and electrical power in an air conditioner?