One method of determining an air conditioner seasonal energy efficiency rating is by manufacture date. Units manufactured prior to 1991 have a SEER of 8 or less while those manufactured between 1992 and 2005 are rated at 10 to 12. Newer models have a minimum SEER of 13 or more.
Units with manufacture dates prior to 1980 have the lowest SEER rating and are less than half as efficient as the newer models. Since the SEER is directly related to energy consumption, these units use more than twice the energy to provide the same amount of cooling.
When purchasing a new air conditioner, the SEER is printed on a label the manufacturer attaches to the device. Generally, units with a higher SEER rating cost more than those with a lower one. However, as of 2015, the Department of Energy requires all units to have a minimum SEER of 13, which also qualifies them as Energy Star rated appliances.
Balancing the climate where installing the unit with the SEER helps to ensure consumers make economical choices. In climates in which air conditioning units are only necessary a few days each year, a lower SEER rating lowers the initial cost. However, in climates in which there are several months of hot weather, selecting a more efficient unit leads to future savings for operating costs.