A one-year operational verification based on building energy management system (BEMS) data was conducted for a large-scale hospital facility in Nagakute City, Aichi Prefecture. The output and energy efficiency of heat source equipment, as well as the stability of supply water temperature, were analyzed. Furthermore, the causes of deviations exceeding 1°C from the set supply water temperature were investigated. The energy efficiency analysis revealed a decrease in the coefficient of performance (COP) for one of two water-cooled chillers. This chiller was relocated from the old facility after one year of use. The decrease in COP was attributed to the use of well water as cooling water at the old facility. The boiler was confirmed to operate inefficiently during summer because of extremely low-load operation. Analysis of flow temperature stability revealed an undesirable operation: the chilled water system flow temperature exceeded the setpoint due to the reverse bypass flow occurring from the return header to the supply header and delayed response to the change in the load of the water-cooled chiller. Similarly, in the hot water system, supply temperature was lower than the setpoint due to the reverse bypass flow and a decrease in the outlet temperature of the heat exchanger with hot water flow restricted in winter. We plan to address with issues that emerge in future.