Definition
EER2 (Energy Efficiency Ratio 2) is the U.S. Department of Energy rating for an air conditioner's or heat pump's cooling output per watt of electricity at one hot test condition, 95°F outdoors, rather than averaged across a season. It describes peak-heat performance. Federal EER2 minimums apply only in the Southeast and Southwest regions.
Also called: Energy Efficiency Ratio 2
Why it matters to you
Washington and Oregon have no federal EER2 minimum, but EER2 describes exactly the afternoons that strain a system here: heat waves like June 2021, when Portland broke its all-time high on back-to-back days. Two systems with similar SEER2 ratings can differ in how efficiently they cool when it is genuinely hot.
Practical guidance
Read EER2 from the AHRI Directory listing for the exact matched indoor and outdoor pair you are quoted. Use it as a tiebreaker between systems with similar SEER2 ratings, not as a legal threshold in WA or OR.
About this definition
Written by the Home Energy Group team — a family-owned HVAC company celebrating 25 years of comfort & care across SW Washington and the Portland metro, licensed in Washington (WA LIC# HOMEEGI003J7) and Oregon (OR CCB# 184255). Definitions inform; an on-site diagnosis decides.
