The efficiency of a split system air conditioner is measured by a Seasonal
Energy Efficiency Ratio (SEER). The higher this ratio, the
more energy efficient the system. The SEER averages a system’s efficiency over the course of one year. It is measured by multiplying 10,200 by the number of tons, or the cooling effect by melting one ton of ice in 24 hours. This number is then divided by the Energy Efficiency Ratio (EER), the amount of heat necessary for raising the temperature of a pound of water by one degree divided by the watts input.
In 2005, a SEER value of 13 was adopted as the government’s base efficiency
level for split system air conditioner efficiency. Many homeowners choose
systems with higher SEER values, however, because of the high cost of energy.