Before buying an air conditioner, it is important to determine not only the design and functionality of the device,but also its power. The power can be calculated by the volume of the room in which the air conditioner is planned to operate. When making calculations, it is important to take into account some nuances, which we will discuss in this article.
We will tell you how to correctly calculate the power of air conditioners and what is important pay attention. In this article, there will be no air conditioner selection calculator, you can easily find it on the Internet.
The main characteristic of any air conditioner is power. The more powerful the device, the larger the area of the room that is planned to be cooled. In this article, we will talk only about one of the possible calculation methods. It is suitable for small rooms (up to 50 square meters).
To calculate the power, use the following formula:
*Q = Q1 + Q2 + Q3*
Q is the power; Q1 is the heat input from the walls and windows; Q2 is the heat input from people; Q3 is the heat input from household appliances.
Q1
To calculate Q1, use this formula Shq/1000 S — room area (in square meters); hceiling height (in meters); qthe coefficient to be selected depending on the room’s illumination (30 for dark rooms, 35 for rooms with medium illumination, and 40 for sunny rooms).
Q2
An adult emits heat energy:

In the absence of physical activity0.1 kW;

When walking0.13 kW;

At physical exertion0,2 kW.
Q3
The computer emits 0.3 kW of thermal energy, and the TV0.2 kW. Most other electrical appliances emit about 30% of their power.
Calculation example
So that you can better understand the specifics of power calculation, we will give a simple example. As an example, let’s take a room with an area of 26 square meters. The standard ceiling height is 2.75 meters. And the room will only accommodate one person, who uses a computer and a small refrigerator. The maximum power consumption of the refrigerator is 165 watts. And the window in the room is located on the sunny side.
First, we need to calculate how much heat energy is released by the walls and windows (Q1). Let’s use the formula we wrote earlier. Our calculation will look like this :
*Q1 = 26 sq. m.\ * 2.75 m*40 / 1000 = 2.86 kW.*
Also, let’s remember about the thermal energy (Q2) that is released by the person living in the room. In the room, he will rest, without physical exertion. Therefore, we will choose a coefficient of 0.1 kW. Do not forget to calculate how much heat energy is released by household appliances located in the the room. The computer allocates 0.3 kW. And the refrigerator emits 0.05 kW., since 0.165 kW*30%/100% ≈ 0.05 kW.
We get that Q3 = 0.3 kW + 0.05 kW = 0.35 kW.
Now we have the ability to calculate the power:
Q = Q1 + Q2 + Q3 = 2.86 kW + 0.1 kW + 0.35 kW = 3.31 kW
So, we learned that to cool a room of 26 square meters with windows on the sunny side, in which one person lives, using a computer and a refrigerator, you will need an air conditioner with a power of 3.31 kW.
Most manufacturers have unified power. Under our requirements , a device with a capacity of 3.5 kW will fit.
What should I pay attention to?
Let’s leave aside the dry calculation and talk about some factors that can affect the selection of power. The above calculations are not perfect. They are more accurate than the choice based on the principle of 1 kW = 10 sq. m. But still not accurate enough to be considered a reference.
Let’s go back to the factors that influence the choice of power. It is important to take into account the amount of air that can enter the room through an open window during ventilation. Our methodology the calculation does not take into account open windows. This is due to the fact that when the air conditioner is turned on, it is not recommended to open the windows.
If you decide to add data about open windows to the calculation, simply increase Q1 by 20% to compensate for the heat load. Also add 15% to Q1 if the room is located on the top floor and there is no cold attic on top.
It is also important to take into account the area of the glazing. In typical houses, the windows are small, but in the new buildings often put large doubleglazed windows in the floor. The amount of natural light entering the room depends on this. In the calculations, we took into account the windows with an area of up to 2 square meters. For each additional square meter, you need to add 100 watts.
Conclusions