EER Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026EER versus SEER
EER measures cooling efficiency at one specific, fixed set of conditions (typically 95 F outdoor temperature), while SEER averages efficiency across an entire cooling season of varying conditions. EER is the figure most relevant to peak-demand performance on the hottest days.
Worked example
For a unit producing 12,000 BTU/hr of cooling while drawing 1,200 watts:
EER = 12,000 / 1,200 = 10.0 EER
Frequently asked questions
What counts as a good EER rating? Modern window units and central systems commonly range from EER 8 up to EER 15 or higher for premium equipment - higher EER means less electricity consumed to deliver the same cooling output.
Why do commercial buildings care more about EER than SEER? Commercial cooling loads and utility demand charges are often driven by peak conditions on the hottest days, making EER (a fixed worst-case efficiency figure) more directly relevant than a seasonal average like SEER.