Cooling Capacity refers to the amount of cooling that a central air conditioner (or a heat pump in cooling mode) can provide. It is most commonly measured as the number of BTUs per hour of heat that the unit can remove from the air. (A BTU or British Thermal Unit) is the amount of heat required to raise 1 pound of water by 1° Fahrenheit.
You may also see cooling capacity rated in tonnage. For example, a contractor may talk about a "3-ton air conditioner". This does not refer to the weight of the air conditioner, but to its cooling capacity.
The term "ton" refers to the approximate amount of cooling power that a ton of ice would provide if it melted over a 24-hour period. One ton is equal to 12,000 BTUh.
Typical residential heat pumps and central air conditioners have a cooling capacity that ranges from about 24,000 - 60,000 BTUs, or 2 - 5 tons.
Performing a Load Calculation
The only accurate way to determine the cooling capacity that you will need in a residential or non-residential air conditioner is to have a heating and cooling contractor perform a load calculation. This is also referred to as "sizing" your air conditioner or heat pump.
A load calculation takes into account many factors, including:
- the size of the building
- the amount of insulation
- the number of windows, and the direction in which they face
- the amount of shade
Why is a Load Calculation Important?
An air conditioner whose capacity is too small will not adequately cool your residence or building. If the capacity is too large, it will cycle on and off too often, decreasing efficiency and increasing your electric bill. In addition, it will not maintain proper humidity levels, resulting in a less comfortable environment.