We know that the air conditioner’s capacity number of tons doesn’t refer to its actual weight. This number actually refers to the amount of heat In British Thermal Units (BTU) the air conditioner system can remove from a house within one hour. One ton of AC capacity is 12000 BTU’s per hour. So why ton you ask, i know your wondering so here we go, believe it or not is based on a 1 ton block of ice which is 2000 pounds.
I will explain, before the invention of refrigerators and air conditioning, people who could afford it, used ice to cool their homes and food. The math is based on the melting (heat transfer) of a 2000 pound block of ice over a 24 hour period at 32 degrees f. If that block of ice melts evenly over the course of the day, it absorbs heat at the rate of 11,917 BTU/hour. Rounded up, we get 12,000 BTU/hour, or one ton of AC capacity.