An energy evaluation tool for chilled water systems was developed. This tool quantifies the energy usage of various chilled water systems and typical energy conservation measures that are applied to these systems. It can be used as a screening tool to identify potential areas that can be further examined while only requiring a minimum number of inputs. The tool is useful for analyzing chiller plants with up to three electric chillers consisting of reciprocating, helical rotary, and/or centrifugal chillers. Both air-cooled and water-cooled systems can be analyzed with the tool, however, this article focuses on water-cooled systems. The tool is capable of analyzing the economics of the following energy conservation measures: 1) raising the chilled water temperature, 2) lowering the condenser temperature, 3) replacing the chiller(s), 4) using variable speed drives on centrifugal compressors, 5) utilizing free cooling, and 6) replacing electric chiller(s) with gas engine centrifugal chillers. For each of these measures, the tool calculates the annual energy and cost savings.