The authors carried out questionnaires and field measurements on the hot water usage and the performance for the CO_2 heat pump (water heater in 14 houses. In this paper, based on the results of the measurements, the behavior of hot water usage and the loads of hot water consumption are analyzed. Especially, as for the loads of reheating bathwater, the relationship between loads and intervals of reheating are shown. And, the authors made a calculation method with calculation process of reheating bathwater. According to the calculation results, some mode of hot water loads for fourteen days were suggested. Finally, the authors carried out experimental evaluation for CO_2 heat pump water heater by using the mode of hot water loads.