IEER (Integrated Energy Efficiency Ratio) measures air conditioning system efficiency across multiple load conditions and outdoor temperatures, providing a more accurate representation of real-world cooling performance than single-point ratings. This metric weights efficiency at 100%, 75%, 50%, and 25% cooling loads across four standard outdoor temperature conditions. IEER accounts for variable-speed compressors and part-load efficiency that single-rating systems cannot capture.
Calculation and Standards
IEER ratings combine efficiency data from different operating points using weighted percentages. Current ENERGY STAR standards require IEER ratings of 13 or higher for residential units and 15 or higher for commercial systems. IEER values typically range from 12 to 25, with higher-efficiency variable-capacity systems achieving superior ratings. The metric uses Btu/h per watt as measurement units.
Practical Applications
IEER provides better accuracy than EER for systems operating below full capacity, which represents typical residential operation. Contractors use IEER ratings to compare equipment efficiency during the specification and selection process. Understanding IEER helps predict cooling costs and system performance across seasons with varying outdoor temperatures and occupancy levels.