Twelve thousand BTUs (British Thermal Units) per hour are equal to 1 ton of cooling capacity. A BTU is the basic measurement of thermal energy.
A British thermal unit is defined as the amount of heat needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit to a specified temperature. Many appliances have BTU ratings, which are often in the thousands. One BTU is an extremely small unit of measurement. Its energy power is about the same as burning one match.
One single BTU can also be expressed as being equal to between 1,054.35 and 1,059.67 joules, another common energy measurement. One BTU is also equal to 252 calories. A calorie is the amount of heat needed to raised 1 gram of water by 1.8 degrees Fahrenheit. One BTU is also equal to about 0.000293 Kilowatt hours.