A distributed auxiliary-power-unit (APU) system for an aircraft includes one or more battery modules for storing electrical power, and a plurality of racks distributed throughout the aircraft for receiving the one or more battery modules to electrically connect with an electrical subsystem of the aircraft. A plurality of hot-swappable racks are adapted to receive the battery modules for electrically and communicatively coupling with the electrical subsystem and an integrated controller. A remote interface is communicatively coupled with the integrated controller for receiving user-input to direct electrical power from the battery modules to one or more subsystems of the aircraft. A number of battery modules installed is based on an amount of electrical power planned for a given flight of the aircraft.