If your existing AC unit is more than 15 years old, it is probably inefficient and you should consider replacing it with a newer, more energy efficient unit. For example, if you replace a 1970s central air conditioning unit that has a SEER of 6 with a new unit and a SEER of 13, you would cut your air conditioning costs in half – or more! Remember, in Arkansas, almost one-fourth of our annual utility costs are paid to keep us cool.