BTU(British Thermal Units)

BTU’s 

- An air conditioner's capacity is measured in “British Thermal Units”, or BTUs. A BTU is the amount of heat required to raise, by one degree, the temperature of a pound of water. So if you buy an air conditioner rated at 10,000 BTUs, it has the ability to cool 10,000 pounds -- about 1,200 gallons -- of water, one degree in an hour. Refrigeration is normally measured in “Tons”. 12,000 BTU’s equal 1 ton.