Energy consumption is minimized in the fuel cell system including a fuel cell 10 having a fuel inlet 14, an oxidant inlet 12, a cathode gas outlet 16 and an anode tail gas outlet 18. At least one humidifier 52,70; 54,72, is interposed between a source of air or fuel and includes an interior energy containing medium flow path 60,61; 62,64; 78,80; 72,84 in heat exchange relation with a reactant flow path 56,58; 74,76 together with a source 46 of water connected to the reactant flow path 56;58; 74,76 to be vaporized therein. The energy containing medium flow path 60,61; 62,64; 78,80; 82,84 is connected to one of the outlets 16,18 to receive a heated fluid therefrom to provide the heat of vaporization to the aqueous material.