BTU: What it is, how it is used in air conditioning, and its equivalence in kW

3 minutes of reading

By Mariona Griera

April 7, 2025

Discover what a BTU is and its importance in climate control. Learn how to convert BTU to kW and vice versa, and how to calculate the necessary capacity for each room. With this guide, choose the right equipment for your air conditioning or heating needs and optimize energy consumption.

In the world of climate control, it is very common to find the unit BTU when talking about the capacity of air conditioning or heating equipment. You have surely seen specifications like “12,000 BTU air conditioner” and wondered what it really means, how it compares to kilowatts (kW) or how many BTUs you need to cool or heat a room. In this article, we clearly explain what the BTU unit is, how it is used, its equivalence with other units like kW, and provide you with a practical guide to calculate how many you need based on the square meters of each room.

What does BTU mean in air conditioning?

BTU are the initials of British Thermal Unit, or British Thermal Unit. It is a unit of energy that indicates the amount of heat a device can extract or provide in an hour. In air conditioning, BTUs are used to express the cooling capacity (in air conditioners) or heating capacity (in heat pumps, for example).

When you see that a unit has 9,000, 12,000, or 18,000 BTU, that means the amount of heat it is capable of moving in one hour. The higher the BTU number, the greater the thermal power of the unit and, therefore, its capacity to air-condition larger spaces.

Although the correct term would be BTU per hour (BTU/h), it is very common to simply indicate the number without specifying "per hour".

What is the difference between BTU and kW?

In Europe, it is most common to use kilowatts (kW) as a unit of thermal power. The good news is that you can easily convert from one unit to another:

1 kW ≈ 3.412 BTU/h
1 BTU/h ≈ 0.293 W (0.000293 kW)

Practical examples

A unit of 12,000 BTU/h has a thermal power of about 3.52 kW
A system of 18,000 BTU/h is equivalent to about 5.27 kW
If a unit offers 3 kW, this translates to about 10,236 BTU/h

This allows you to easily compare equipment that is labeled in different units, something common when working with international products.

How to convert BTU to kW and kW to BTU?

Very simple:

To convert from BTU to kW, multiply the BTU by 0.000293
To convert from kW to BTU, multiply the kW by 3.412

Example:

9,000 BTU × 0.000293 = 2.63 kW
3.5 kW × 3,412 = 11,942 BTU

These types of calculations are useful for choosing the right equipment based on your air conditioning needs.

How many BTUs do I need for a room?

One of the most common questions is: How many BTUs do I need for X square meters?. Although there are several factors that influence (insulation, orientation, number of people, etc.), here is a guideline table:

Room area	Recommended BTU	Approximate power (kW)
10 m²	~5,000 BTU/h	~1.5 kW
15 m²	~7,500 BTU/h	~2.2 kW
20 m²	~10,000 BTU/h	~2.9 kW
30 m²	~12,000 BTU/h	~3.5 kW
40 m²	~16,000 BTU/h	~4.6 kW
50 m²	~20,000 BTU/h	~5.8 kW
60 m²	~24,000 BTU/h	~7.0 kW

These values are a standard reference, but they may vary depending on the actual conditions of the room.

Factors that influence the choice of BTU

Orientation and direct sunlight: if the room receives a lot of sun, add an extra 10-15% capacity.
Ceiling height: if it exceeds 2.5 meters, adjust upwards.
Number of people: add about 600 BTU for each additional person beyond the usual two.
Electronic equipment or kitchen: if the space has many devices or is a kitchen, add about 1,000 to 4,000 more BTU.

Conclusion

Knowing what a BTU is and how it compares to kW allows you to make better decisions when choosing an air conditioning or heating unit. Whether you are installing a system in a home, store, or industrial warehouse, accurately calculating the thermal capacity will prevent poor performance or excessive consumption.

In summary:

BTU measures thermal capacity per hour.
1 kW ≈ 3.412 BTU/h.
To estimate the necessary power, calculate between 400 and 520 BTU per m² as a base.
Adjust the capacity according to the conditions of each room.

Are you looking for equipment with the right capacity for your project? At GroupSumi, you will find professional climate control solutions, with detailed technical descriptions in BTU and kW to facilitate your choice.

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