A power supply system comprises a chargeable power storage device; a charging device configured to perform external charging for charging the power storage device using alternating-current power supplied from an external power supply; an air conditioner receiving electric power from the charging device and the power storage device and air-conditioning a compartment in a vehicle; an auxiliary machinery load; and an ECU. The ECU controls at least one of the charging device and the auxiliary machinery load so as to increase the electric power output from the power storage device in a case where overcharging of the power storage device is expected when the air conditioner is intermittently operated during external charging.