SEER Ratings Explained

SEER stands for Seasonal Energy Efficiency Ratio, and it measures the total cooling output of an air conditioner during a typical cooling season divided by the total electrical energy input over that same period. Higher SEER means more cooling per watt-hour. The minimum SEER allowed by federal regulation has crept upward over the years; new units sold today must meet 14 SEER in the northern US and 15 SEER in the southern US, with even higher minimums for heat pumps.

Mainstream residential air conditioners run 14-22 SEER. Premium variable-speed units reach 25+ SEER but cost two to three times as much as a 14 SEER baseline unit. The energy savings between 14 and 18 SEER are substantial in hot climates with long cooling seasons (Texas, Florida, Arizona), modest in moderate climates (Mid-Atlantic, Pacific Northwest), and barely noticeable in cool summer climates (Northern New England, Pacific Coast).

SEER2 is the updated test methodology that took effect in 2023. The numbers are about 4.5% lower than the old SEER for the same unit, which is purely a measurement change rather than a real efficiency drop. When comparing units, make sure you are comparing SEER to SEER and SEER2 to SEER2.

Other ratings on the data plate matter too. EER (Energy Efficiency Ratio) measures efficiency at a specific outdoor temperature — useful for comparing how a unit performs on the hottest days. HSPF (Heating Seasonal Performance Factor) measures heat pump heating efficiency. AFUE (Annual Fuel Utilization Efficiency) measures gas furnace efficiency. The Energy Guide label on a new unit summarizes all of these and gives an estimated annual operating cost based on national average utility rates; for an honest comparison, redo the math with your local utility rates.