The present invention relates to a power supply device and a power supply system including the same. The power supply device includes a first connector to receive an input alternating current (AC) voltage, a second connector to output a first output AC voltage to a grid, a third connector connectable with a plug of an external electronic device, a voltage conversion unit to convert a first direct current (DC) voltage stored in a battery into an AC voltage, and a controller configured to control the first output AC voltage based on the input AC voltage not to be supplied to the grid when grid power outage occurs while the first AC voltage is output to the grid, and control the input AC voltage to be output to the third connector as a second output AC voltage, or control the input AC voltage to be converted into the first DC voltage and the first DC voltage to be supplied to the battery. Thereby, the input AC voltage generated by the solar module may be utilized when grid power outage occurs.