Most air conditioning units have their capacity rated or specified in BTU (British thermal units).
BTU, generally speaking, is the amount of heat needed to increase the temperature of one pound (or 0.45 kg) of water by one degree Fahrenheit (or 0.56 degrees Celsius). Specifically, 1 BTU equates 1,055 joules, whereas in heating and cooling terms, 1 “ton” equates 12,000 BTU.
A typical mono-bloc air conditioning unit might be rated or specified at 10,000 BTU. For basic comparison, a typical 2,000 sq. ft. (185.8 m2) house might need a 5-ton (60,000 BTU) air conditioner. It implies that you might require perhaps 30 BTU per sq. ft. for 100 watts per square metre.
Keep in mind that these are approximate calculations. You need to get in touch with experts to know the correct size of an air conditioner for your specific cooling needs, depending on the area to be cooled.
Another important consideration is EER or the energy efficiency rating. An air conditioner’s energy efficiency is its ‘BTU rating over its wattage’. For instance, if a 10,000-BTU air conditioning system consumes about 1,200 watts, the EER works out to 8.3 (10,000 BTU/1,200 watts=8.3). Obviously, a user would like the EER rating to be as high as possible.