A new federal regulation will help rein in mounting energy costs. As of January 2006 manufacturers can no longer produce residential central air conditioners with efficiencies less than 13 SEER. The minimum Seasonal Energy Efficiency Ratio, or SEER, is up from 10, which was in place since 1992. Basically, the higher the SEER rating, the more energy efficient the central air conditioning unit and the less electricity you'll need to cool your home.