A power usage management system includes, in order to efficiently distribute electric power, a power feeding gate device supplied with electric power from a power line and controlling supply of electric power based on a key code, a server system transmitting a key code corresponding to identification information for identifying the power feeding gate device, and a mobile receptacle attachable/detachable to/from the power feeding gate device, receiving identification information from the power feeding gate device, receiving the key code corresponding to the identification information from the server system, and providing the key code to the power feeding gate device.