The present disclosure relates to a method for determining an efficiency curve of a chiller that includes operating a chiller over a range of operating capacities, measuring a temperature of water entering the chiller at an initial capacity, measuring a temperature of water exiting the chiller at the initial capacity, measuring a power consumption of the chiller at the initial capacity, calculating an initial efficiency of the chiller at the initial capacity, measuring a plurality of temperatures of water entering the chiller at a plurality of capacities, measuring a plurality of temperatures of water exiting the chiller at each of the plurality of capacities, measuring a plurality of power consumptions at each of the plurality of capacities, calculating a plurality of efficiencies at each of the plurality of capacities, and generating an efficiency curve for the chiller with the initial efficiency and the plurality of efficiencies.