An array of fuel cell systems are electrically couplable in series and/or parallel combinations to provide a variety of output powers, output current and/or output voltages. The fuel cell systems are "hot swappable" and redundant fuel cell systems may automatically replace faulty fuel cell systems to maintain output power, current and/or voltage, with or without switching. The configuration of fuel cell systems may be automatic and may be based on desired power, current and/or voltage, and/or based on the operating parameters of the fuel cell systems and/or power supply system.