A power system of a ship includes a first power storage device, a second power storage device, and a control system. The first power storage device has an energy density higher than that of the second power storage device. The second power storage device has a power density higher than that of the first power storage device. The control system is configured to: as a power generator application, prioritize discharging the first power storage device over discharging the second power storage device, such that base power is continuously supplied to an onboard electrical load connected to an onboard bus; and as a grid stabilization application, prioritize charging/discharging the second power storage device over charging/discharging the first power storage device to compensate for frequency variation or voltage variation of an onboard power grid.