Air conditioners and heat pumps come in different sizes based on the heating or cooling load of homes and buildings. Central air conditioners are defined by tons, and heat pumps are defined by kilowatts. Converting from one to the other is easy, but the process involves finding the exact sizing of the unit. That can be challenging if the user manual or unit does not specify the size of the heat pump.
Look for the kilowatt rating of your heat pump on the compressor outdoors or on the air handler. If you can't find the information anywhere, look for the model number. It may be printed on a tag on the compressor or the air handler. Write down the number.
Find the instruction book that came with the heat pump. The specifications page may indicate how many kilowatts the heat pump uses. If there is no mention of the size, call the manufacturer or installer with the model number. Installers and manufacturers keep model lists for maintenance and repair purposes.
Convert the kilowatt rating of your heat pump to British thermal units (BTUs). Multiply the kilowatt rating by 3,414.45, the number of BTUs in a kilowatt. Divide the result by 12,000, the number of BTUs in a ton. For example, a 5-kw heat pump has 17,072 BTUs. Dividing the BTUs by 12,000 yields 1.42 tons. The size of this heat pump would be close to 1.5 tons.