FUEL CELL SYSTEM

A fuel cell system (1) includes: a fuel cell (34) generating power by fuel and oxidizer gas; a reforming unit (33) generating the fuel from a reforming raw material and reforming water and supplying the fuel to the fuel cell; a combustion unit (36) introducing combustible gas containing unused fuel from the fuel cell thereinto, burning the combustible gas, and leading out the combustion exhaust gas; a hot water storage tank (21); a heat exchanger (12) exchanging heat between the combustion exhaust gas and stored hot water, condensing water vapor in the combustion exhaust gas, and producing condensed water; a stored hot water circulation line (22) circulating the stored hot water; a delivery device (22b) provided in the stored hot water circulation line and delivering the stored hot water; a heat exchanger stored hot water outlet temperature sensor (22d) detecting the temperature of the stored hot water; and a control device (15) controlling the delivery quantity of the delivery device.