EER2
energy efficiency ratio 2 · EER
EER2 (energy efficiency ratio 2) is the federal rating of an air conditioner's or heat pump's cooling efficiency at peak load, 95 °F (35 °C) outdoors: cooling capacity in Btu per hour divided by power input in watts.
DOE describes EER as a measure of peak load efficiency, the efficiency of a system when it is working its hardest. EER2 is the same kind of metric measured under the revised test procedure required since January 1, 2023, and is not directly comparable with the older EER.
Where SEER2 averages over a season, EER2 describes one hot condition. DOE notes it matters most in hot-dry climates, where air conditioners work hard on many days. That is why the Southwest region has EER2 minimums for central air conditioners as well as SEER2 minimums: for split systems under 45,000 Btu/h, 11.7, or 9.8 for models with SEER2 of 15.2 or more.
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