A power conditioner includes first and second power conversion portions, a smoothing capacitor, and an auxiliary power supply. The first power conversion portion is connected to a DC system. The second power conversion portion is connected to an AC system. The capacitor is connected between wires of an intermediate bus which connects input/output terminals of the first power conversion portion and the second power conversion portion. The auxiliary power supply receives commercial power and generates an auxiliary charge voltage to be applied to the capacitor. The first power conversion portion converts DC power of the storage battery to a first DC voltage and outputs the first DC voltage to the intermediate bus. The second power conversion portion converts a voltage of the capacitor to an AC voltage and outputs the AC voltage to the AC system. The auxiliary charge voltage is lower than the first DC voltage.