Abstract: A storage unit for a consumer is described, having an energy storage in which electric energy can be stored, and a current interface via which the storage unit can be connected to an electricity grid. The storage unit furthermore has a circuit arrangement which is arranged between the energy storage and the current interface in the direction of current flow, and a control interface for controlling the storage unit. The storage unit is controllable only via the control interface which communicates only with an external control. A storage system and a method of controlling a storage system are furthermore described.