An array of photovoltaic (PV) module(s) is arranged in series and/or parallel electrical connection to deliver direct current electrical power to an electrolyzer to produce hydrogen. The electric power is delivered by the array at its maximum power point (Vmpp) to deliver Ioper at Voper for the electrolyzer. The arrangement of the PV modules in the array, or the arrangement of cells in the electrolyzer, is continually monitored and controlled by an automatic controller system to operate the PV and electrolyzer systems at or near their respective maximum efficiencies. A DC-DC converter may be used to adjust the Vmpp to the operating voltage of the electrolyzer.