A modular power supply apparatus including a base part and a portable part couplable thereto and detachable from the base part, wherein the portable part comprises an energy storage device or a first energy storage element of the energy storage device and a first output, and the portable part is configured such that the energy storage device or the first energy storage element can supply the first output with an electrical voltage, the base part comprises a grid connection, a switching device or a part of same and a second output, and the energy storage device or the first energy storage element of the energy storage device is electrically connected to the switching device in the event of the portable part having been coupled.