A carriable power transfer unit that can be used for bidirectional power transmission between a power network and each of the plurality of vehicles provided with driving power sources is provided. The power transfer unit includes: a plurality of connecting portions that are attachable to and detachable from each of the plurality of vehicles, and are used for power transmission between the power transfer unit and each of the plurality of vehicles; and a control unit that controls bidirectional power transmission between the power network and each of the plurality of vehicles.