A power inverter device includes an inverter that converts a direct-current (DC) power to an alternating-current (AC) power having an output AC voltage, and a capacitor circuit electrically connected to the inverter. The capacitor circuit is operable to start supplying a capacitor voltage to the inverter at a time point when a predetermined waiting time lapses from a zero cross point of the output AC voltage at a starting up of the inverter circuit, wherein the capacitor voltage has a phase shifted by π/4 radian from the output AC voltage. The inverter is operable to generate the output AC power based on the capacitor voltage and the DC power. The predetermined waiting time is a duration is equal to 2πn+3π/4 radian or 2πn+7π/4 radian of a phase of the output AC voltage (n is an integer not smaller than zero). This power inverter device can reduce a ripple power of the input power early after the starting-up.