Applications:
In considering chiller improvements, first cost and operating costs must be compared. The higher the number of hours and cost of electricity, the shorter the payback period during which energy savings will compensate for the added cost of more efficient equipment. For new installations, high-efficiency machines should be considered if they are expected to operate over 1,000 hours per year.

Older chillers may benefit from replacement or retrofitting. In general, chillers that operate more than 4,000 hours per year in areas with electricity rates over $0.07/kWh are good candidates for replacement based on energy costs alone, but other benefits include reduced maintenance and less costly refrigerants. Chillers over 20 years old are good candidates for replacement because they are nearing the end of their useful life and significantly less efficient than new models. Chillers less than 20 years old may be improved designs, and should be considered on a case-by-case basis. Chillers with higher operating hours per year are better economic candidates for replacement.

Chillers that cannot be economically replaced may still be good candidates for retrofitting. This process could include installing better controls, trimming impellers, and other adjustments. The most advantageous time for retrofitting is during a scheduled maintenance. Any chiller using older refrigerants such as R-11 and R-12 containing CFC should be considered for refrigerant replacement. The older types of refrigerants (Class 1 ozone depleting) are no longer produced due to negative environmental impacts and are thus becoming more expensive, difficult to obtain, and involve strict regulations on handling and storage.

Performance:
Chiller efficiency is measured in terms of electrical use per ton of cooling (ton). Chillers are rated at full load efficiency, application part load value (APLV), and integrated part load value (IPLV). The latter two values are generally more useful because chillers operate primarily at part load.

Source: U.S. DOE, Federal Energy Management Program High Efficiency Centrifugal Chillers