There are three main ways to determine the SEER of equipment: (1) find the model numbers of your present equipment and check them with a local contractor (such as Wall-Turner Company). (2) estimate the SEER based on the average SEER units produced approximately when your system was installed. (3) check the energy efficiency label on your outdoor unit if it was produced after 1989.
In the first method, contractors can then consult manufacturer data or the ARI directory which lists all models of equipment by manufacturers that certify their equipment.

In the second method, for air conditioners and heat pumps produced in 1981, the first year SEER criteria was used, the average ratings were 7.78 (A/C) and 7.51 (H/P) respectively. By 1987, SEERs reached 8.97 and 8.93 respectively.

By 1994, ratings increased to 10.61 for air conditioners and 10.94 for heat pumps.

Remember that The National Appliance Energy Conservation Act of 1987 set a federal standard of 10.0 SEER minimum for air conditioners and heat pumps made after January 1992. The fact that, two year later, the average was 10.61 shows that the best air conditioners available were only slightly better than 11 SEER in 1994.

In the third method, residential central air conditioners and heat pumps covered under Department of Energy test procedures and manufactured on and after June 7, 1988, are required to have labels containing energy efficiency information.