A floating photovoltaic power system is a power generation system that floats on the surface of water. Owing to its floating characteristics, the structure moves as the water level changes. In this study, we investigated whether the changes in water level affect the amount of power generated by the floating photovoltaic power system. We selected floating solar power plants that are currently in operation and analyzed the annual/monthly utilization rates. Our results confirmed that the utilization rate of the floating photovoltaic power system installed in areas with marked changes in water level is the lowest. In addition, correlation analysis of environmental factors that affect power generation such as solar radiation, temperature, humidity, wind speed, and water level confirmed that changes in water level resulted in decrease in power generation.