A power source apparatus that combines power generated by a photovoltaic system and power generated from another power source by using a power combiner and transmits the combined power to a load side, wherein an output voltage of the photovoltaic system can be changed by changing a cell connection state of a plurality of solar cells of the photovoltaic system, and the highest efficiency of the photovoltaic system can be obtained by adding the output voltage of the photovoltaic system to an output voltage of the another power source.