Energy Efficiency Ratio (EER) measures air conditioning cooling output in BTU per hour divided by electrical power consumption in watts at a single operating condition of 95 degrees Fahrenheit outdoor temperature and 80 degrees indoor temperature. This full-load rating provides a simple baseline comparison between cooling systems. EER values typically range from 8 to 15, with higher numbers indicating greater efficiency.
Testing and Standards
EER is determined under specific laboratory conditions defined by AHRI standards, making it useful for direct equipment comparison. Modern residential air conditioners typically achieve EER ratings between 10 and 13. EER focuses on full-load performance, which represents only 15% to 20% of actual annual operation, limiting its predictive value for real-world energy consumption.
Limitations and Practical Use
EER alone cannot predict seasonal cooling costs because most systems operate below full capacity. Contractors supplement EER with SEER or IEER ratings for accurate efficiency assessment. Understanding both EER and seasonal ratings provides comprehensive equipment evaluation. EER helps identify whether systems maintain efficiency across temperature ranges, while seasonal ratings predict annual operating expenses more accurately.