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EER2

EER2 is a cooling efficiency rating at a single hot test condition, in Btu per hour of cooling per watt.

Editorial staffEdited by heatpumpwiki

History 1

EER2 (Energy Efficiency Ratio 2) is cooling capacity divided by power input at one test condition, in Btu/h per watt.Source 1 SEER2 averages over a season; EER2 describes performance at one hot condition. NRCan describes EER as describing "the steady-state cooling efficiency of a heat pump."Source 2

EER2 matters most in hot climates. Federal Southwest standards for central air conditioners include EER2 minimums.Source 3 ENERGY STAR Version 6.2 requires an EER2 of 11.0 or more for split heat pumps.Source 1 See Heat pump ratings explained: SEER2, EER2, HSPF2 and AHRI certificates.

Sources

  1. 1.ENERGY STAR Program Requirements for Air Source Heat Pumps, Version 6.2 (Rev. February 2, 2026). ENERGY STAR (U.S. EPA and DOE). Accessed Oct 25, 2026
  2. 2.Heating and cooling with a heat pump. Natural Resources Canada. Accessed Oct 25, 2026
  3. 3.10 CFR 430.32, Energy and water conservation standards and their compliance dates. Electronic Code of Federal Regulations (U.S. DOE rule). Accessed Oct 25, 2026

More in Glossary

  • AHRI certificateAn AHRI certificate shows the certified efficiency ratings for one exact combination of outdoor and indoor heat pump equipment.
  • Aux heat (auxiliary heat)Aux heat is a backup heat source that a heat pump thermostat turns on automatically when the heat pump needs help.
  • Btu (British thermal unit)A Btu is the heat needed to raise one pound of water by one degree Fahrenheit, and heat pump capacity is given in Btu per hour.
  • COP (coefficient of performance)COP is the heat a heat pump delivers divided by the electricity it uses, at one set of conditions.
  • DefrostDefrost is the cycle in which a heat pump briefly reverses to melt frost off its outdoor coil.
  • Emergency heatEmergency heat is a thermostat mode that turns the heat pump off and heats with the backup source only.