How to calculate chiller power consumption
In US practice chiller efficiency is quoted as kW/ton, the kilowatts of compressor input needed per ton of refrigeration, where one ton equals 12,000 BTU/hr. Power draw is simply capacity in tons multiplied by kW/ton, which is why the metric is so convenient on a plant schedule. Unlike COP or EER, a lower kW/ton is better, so watch the direction when you compare products.
The three efficiency metrics all describe the same machine. COP = 3.5168 ÷ (kW/ton) and EER = 12 ÷ (kW/ton), so a chiller at 0.60 kW/ton has a COP near 5.86 and an EER of 20. Water-cooled centrifugal machines commonly land between 0.50 and 0.65 kW/ton at full load, water-cooled screw units around 0.65 to 0.80, and air-cooled packages usually above 1.0 kW/ton because the condenser rejects heat to ambient air rather than to a cooling tower.
Annual energy is estimated as full-load kW times operating hours times the average load factor. Real chillers often run more efficiently at part load, so for a rigorous comparison look at IPLV or NPLV, the part-load weighted values published under AHRI Standard 550/590, alongside the full-load number. Treat the cost figure here as a planning estimate, since demand charges and time-of-use rates can shift the actual bill considerably.
Frequently asked questions
They are the same efficiency expressed three ways: COP = 3.5168 divided by kW/ton and EER = 12 divided by kW/ton. A chiller at 0.60 kW/ton is roughly COP 5.86 and EER 20.
Full-load efficiency describes one operating point. Chillers spend most hours at part load, so the weighted IPLV or NPLV value tracks annual energy cost much more closely.