Wonder Why an Air Conditioner’s Capacity is Measured in Tons?

Have you heard someone talk about an air conditioner in terms of tons and wonderered what that really means? It may sound like the actual air conditioner unit may weigh 3 or 4 tons, but that is absolutely not the case…thank goodness. That measurement is an estimate of how much heat, per hour, can be extracted from your home with a particular unit.So what does a ton of heat mean and why do they measure it that way? Well, it actually goes back to the 1800’s when blocks of ice were taken from frozen lakes and rivers to be stored and used to cool buildings in the summer. Using physics, the amount of heat required to melt a pound of ice is 143 BTU or British Thermal Units. You multiply that by 2,000 pounds, or a ton and then divide the result by 24 ( the number of hours in a day). That roughly translates into 12,000 BTU’s of heat to melt a ton of ice in an hour. To put that in today’s terms, a one -ton air conditioner will extract 12,000 BTU’s of heat from the air per hour, while a 3-ton unit will extract 36,000 BTU’s.
There’s a lot more involved than melting ice to determine what size air conditioner your home needs to stay cool. These factors include square footage, outside air temperature,humidity levels, occupancy, and insulation and air leakage. A system that is too big or too small will cost you more money. A small system is cheaper to buy, but if the unit is too small, it will have to work harder to maintain your thermostat settings. This will increase your energy costs and shorten the life of the unit. A large air conditioner is more expensive, but if it is too large, the system will begin to short-cycle and this will use more energy thasn it should.
To make sure you get the proper size air conditioning unit to properly cool your home and remain energy efficient, it is essential to have it properly sized. A heating and air estimator can determine exactly the size unit you should have installed to remain comfortable and achieve energy efficiency. If you are thinking about having your current system repalced, give MTB Heating and Air a call. Our estimator can help you make the right decision about which unit is the right choice for you. You can also visit our Energy Savings Caluculator on the web to determine the energy savings you can get with a new high efficiency unit.