Integrated part-load value (IPLV) is a widely used keyindex for evaluating the part-load performance of water chillers.However, there are still some disputes on its rationality. Inthis paper, by analyzing the physical nature of seasonal performance,a new index, the seasonal part-load value (SePLV), isproposed to reflect the seasonal performance of water chillersmore accurately. Furthermore, IPLV and SePLV metrics arecompared in the aspects of formula form, value and application.