SEER (Seasonal Energy Efficiency Ratio) was the primary efficiency rating for air conditioners and heat pumps in the United States from the 1990s through 2022. It measures the total cooling output of a system during a typical cooling season divided by the total electrical energy consumed.
SEER was calculated under test conditions that did not adequately reflect real-world installation performance. In 2023, DOE replaced SEER with SEER2, which uses a revised testing methodology (M1 blower coil) with higher external static pressure that better reflects actual installed conditions. SEER2 ratings are typically 4-5% lower than equivalent SEER ratings for the same equipment.
Equipment manufactured before 2023 will still display SEER ratings. When comparing older SEER-rated equipment to new SEER2 equipment, multiply the SEER2 rating by approximately 1.046 to convert to an equivalent SEER value for comparison. The minimum SEER2 for new equipment replaced the old 13 SEER minimum as of January 1, 2023.