Air conditioning has come a long way since its first appearance on the market as a cooling device for buildings and homes. In the year 2000, air conditioners used from 30% to 50% less energy than models manufactured in the 1970s. With newer models, makers have found ways to design them for better efficiency.
Before talking about the amount of energy used up by air conditioning, it is important to know how they work. An air conditioner works in a similar manner to a refrigerator, in that a pump and a circuit of tubes create the cooling system. Inside the device is serpentine tubing, often composed of copper, that winds into two types of coils, evaporator coils and condenser coils. The cold, indoor evaporator coil cools the room while the hot, outdoor coil releases heat outside. The collected heat that is expelled is a result of the energy running through the machine as it does its job.
Also inside the air conditioner is a pump also known as a compressor. This pump moves a heat transfer fluid, called refrigerant, between the condenser and the evaporator. Both kinds of coils are surrounded by aluminum fins, and the compressor forces the heat transfer liquid through the series of tubing and fins. The liquid evaporates when it hits the evaporator, drawing heat out of the indoor air, resulting in the perceivable decrease in room temperature. This gaseous refrigerant is then pumped to the condenser, where it condenses into a liquid again, expelling heat.
Ratings for air conditioning run by the number of British Thermal Units (BTU) an air conditioner can remove per hour, with 12,000 BTU equaling a ton. The energy-efficiency rating is measured by dividing the BTU per hour by the number of watts the air conditioner consumes. The final number is the Energy Efficiency Ratio (EER), which is used to characterize the efficiency of the system; that is, a higher number means better efficiency. In the US, all air conditioners being manufactured today must sport an Energy Guide Label somewhere visible on the machine. In general, a more expensive air conditioner carries a higher EER, which is a worthy initial investment considering its frequent utilization and lower electricity consumption rate.
A regular air conditioner for the home usually has a 5,500 BTU to 14,000 BTU per hour range. Room air conditioning devices built after 1 January 1990 have been subject to US national appliance standards of an 8.0 EER. The hotter the climate a home is in, the higher EER is recommended to be. As a result, homeowners living in homes in hot climates should seek to purchase an air conditioner with at least a 10.0 EER.
People who have air conditioners in their homes can cut down on energy costs by turning the system on only when there are people at home. Air conditioners cool the air fairly quickly, so they should only be turned on when necessary. Homeowners should keep drapes or blinds closed on the windows that face the sun, which reduces the amount of solar heat entering rooms. It is also a good decision to install a programmable thermostat, so that the home is cooled on a routinely basis and saves the homeowner the trouble of manually turning it off and on every time he leaves and comes home.