FUEL CELL SYSTEM

A fuel cell system (1) includes: a fuel cell (34) that generates power by fuel and oxidizer gas; a reforming unit (33) that generates the fuel from a reforming raw material and reforming water and supplies the fuel to the fuel cell; a combustion unit (36) that introduces combustible gas containing unused fuel from the fuel cell thereinto, burns the combustible gas using oxidizer gas, and leads out the combustion exhaust gas; a hot water storage tank (21) that stores stored hot water; a heat exchanger (12) that performs heat exchange between the combustion exhaust gas and the stored hot water, condenses water vapor contained in the combustion exhaust gas, and produces condensed water; a stored hot water circulation line (22) for circulating the stored hot water between the hot water storage tank and the heat exchanger; and a control device (15) that integrally controls the fuel cell system.