FUEL CELL SYSTEM

A fuel cell system is provided that can operate continuously and appropriately when a water self-sustaining operation of the fuel cell system is difficult due to environmental conditions and operating conditions, etc. When a first water level corresponding to a water shortage in a condensed water tank is detected using a water level detector, a controller implements a water-saving mode where the output of a fuel cell is decreased regardless of the external power load and the amount of reforming water used is reduced. When it is determined using a cooling determination device during the water-saving mode that the exhaust gas cooling capability in a condenser brought about by a cooling medium is at least a prescribed value, the controller implements a water recovery mode where the output of the fuel cell is increased regardless of the external power load and the amount of condensed water recovered is increased.