What is BTU of an air conditioner? Calculation

Considering that the main function of the air conditioner is cooling the room, so first of all you need to pay attention for cooling power. The required air conditioning capacity is calculated according to the parameters of the premises for which it is selected. Often confused the power of cooling and power  of consumption. In fact, the power consumed by air conditioning, several times less cooling power, so the air conditioning capacity of 2 kW will consume about 700 watts. The ratio of the cooling capacity to the power consumption of air conditioning is called energy efficiency and in the table refers to the EER (for room air conditioners is 2.5 – 4).


It is very important to choose the necessary power conditioner. If the air conditioner power is insufficient – it can happen that there is no possibility for AC to cool the room (especially in the summer heat). But also do not need to buy air conditioning with excess capacity. The more powerful air conditioning, the more expensive it and consumes more electricity and also device will often turn on and off, which will ultimately lead to a reduction in its service life.

Here we will show you 2 ways to calculate the power conditioner:

  1. How to calculate the power
  2. How to determine the capacity of the air conditioner based on features of the room.

For a rough estimate – count about 1 kW of cooling capacity at 25-30 m3 of space (it is approximately the same as 1 kW of cooling capacity at 10 m2).

How much BTUS needed to cool a room?

There is technical characteristics in our website where you can find the cooling capacity in kW and labelling of air conditioning  – numbers 07, 09, 12. For example, the Hyundai conditioners referred to as HS / HU-09H99X, HSI / HUI-12H99X etc. This marking is used in accordance with the gradation BTU (BTU – Britain Thermal Utility):

  • 2.0 kW – the so-called “Seven” (7000 BTU)
  • 2.5 kW – “Nine” (9000 BTU)
  • 3.5 kW – “The Twelve” (12000 BTU), and so forth.

You can use the data of the following table to calculate cooling BTU of needed air conditioner:

BTU kW sq m
5000 1,6 up to 16
7000 2 up to 20
9000 2,6 up to26
12000 3,5 up to 35
18000 5,2  up to 52
24000 7 up to 70
30000 8 up to 80

The first column it is a BTU gradation, the second column “kW” contains the average cooling performance by producers. In the third column are listed btu and room sizes, its recommendations for space when the window is not located on the sunny side or good blacked out. Also its not recommended to stay in the room a lot of people, and the fuel equipment.

Typically, for a room area of ​​up to 18 – 20 m2 you can buy so-called “Seven” (7000 BUT), to fit 25-27 m2 “Nine” (9000 BTU) and so on. Let’s say you have three rooms for 15, 20 and 25 square meters. Most likely, you will need two “Seven” and a “nine”. If the room is 20 sq.m. south-facing, then it is better to choose the “nine”.

Calculation of power conditioner for the specific premises

To perform an accurate calculation of the power conditioner, you should take into consideration  features rooms (heat gain, heat loss and airflow). To calculate the power of the air conditioner you should have answers for the following questions:

Type of room for AC (domestic room, office or shop)

For each of the above types of premises have their own feature and placement of the air conditioner (for example, do not buy a mobile air-conditioning in the bedroom due to loud noise). Some common cases there are ready-optimal solutions, for example for one-bedroom apartment with a standard layout will fit wall multi split-system air conditioner with blocks of different capacities.

Purpose of air conditioner

Some air conditioners can only cool the room, while others may still perform heating. Typically, the air conditioner does not ventilate the room, its only cools / heats the air, which is in the room. But some types (e.g ducted air conditioning) can supply fresh air.

Room space

What is the area of the room is used for a rough estimate of the cooling capacity.

Quantity of individual rooms

How many separate rooms in your apartment (office, shop)?

Only some types of air conditioners are able to condition several rooms simultaneously. This household wall multi split system or semi-industrial air conditioners.

Equipment that generates heat

The generated heat of that  equipment will have to compensate by increasing cooling capacity of the air conditioner. The additional heat generated in the winter, is not so important – just turn on the heating at lower power.

Windows orientation and shading

A large window without curtains, oriented to the south, creating a much larger heat gain from solar radiation than the closed shutters and small window oriented to the north.

Approximate number of people in the room

Man devotes about 100 watts of heat. Therefore it is necessary to consider this factor in the power calculation.

All these data are essential. A good specialist with the information described above, will be able not only to calculate the cooling capacity, but also choose the type of air conditioner,  basic functions of it and estimated installation configuration.

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