How to Calculate the Power of an Air Conditioner in BTU for a Specific Area

To calculate the capacity of an air conditioner in BTU (British Thermal Units) , and considering that you want to use metric units for other elements of the calculation, we can proceed as follows:

1. BTU concept

• BTU is a unit that measures the amount of heat required to raise the temperature of 1 pound of water by 1 degree Fahrenheit . In terms of air conditioning, BTU indicates the amount of heat that the air conditioner can remove from a room in one hour.
• To calculate the required capacity in BTU , the basic value is 600 to 800 BTU per square meter (m²) for an environment with normal characteristics, that is, without direct sunlight or many electronic devices.

 

2. Calculating the Power of an Air Conditioner in BTU

To calculate the required cooling power in BTU/h for a specific area (in square meters), the basic formula is:

Capacity in BTU/h = Area (m²) × 600 (BTU/m²)

In other words, an area of ​​1 m² requires 600 BTU per hour. For spaces with a high thermal load (intense solar exposure or a lot of equipment), up to 800 BTU/m² can be used.

 

3. Calculation Example:

For a 20 m² room:

Capacity in BTU/h = 20 m² × 600 BTU/m² = 12,000 BTU/h

Therefore, to adequately cool a 20 m² room, you would need an air conditioner with 12,000 BTU/h .

 

4. Special Condition Adjustments

The air conditioning capacity must be adjusted if there are additional factors such as:

THE  High Sun Exposure : If the environment has high sun exposure, add 20% to 30% to the capacity.

Example Adjustment = 12,000BTU/h × 1.30 = 15,600 BTU/h

 

THE  Number of occupants : For each additional person beyond the second, add 600 to 800 BTU/hr . If there are more than 2 people, adjust as needed.

 

THE  Electrical equipment : Add 1,000 to 1,500 BTU/hr for heat-generating equipment such as computers, televisions, or stoves.

 

Example: If the 20 m² room has 2 additional people and a high-performance computer:

Total Adjusted Capacity = 12,000 BTU/h + 2 × 600 BTU/h + 1,200 BTU/h (computer) = 14,400 BTU/h

 

5. Cooling Power by Area Size Table

Area	Required capacity
10 m²	6,000 BTU/h
15 m²	9,000 BTU/h
20 m²	12,000 BTU/h
25 m²	15,000 BTU/h
30 m²	18,000 BTU/h
40 m²	24,000 BTU/h
50 m²	30,000 BTU/h
60 m²	36,000 BTU/h

 

The air conditioning capacity should be chosen based on the size of the room, specific characteristics (sun exposure, equipment, etc.) and the number of occupants.

European standards such as EN 14511 and EFEC (European Federation of Air Conditioning, Ventilation, and Refrigeration) guidelines can also be useful for confirming the exact specifications for HVAC systems, should you require additional details.

Author: Eng. Francisco Quisele Jr.

Date of publication : 11/21/24