Device for determining and/or controlling an operating time of a consumer coupled to a power plant, in particular photovoltaic power plant, and an energy storage device, and method for operating an energy storage device coupled to a power plant

The device (1) has a first detecting unit (3) to determine the amount of power generated by power plant (2). A second detecting unit (4) determines the power consumption of load (5). A third detecting unit (6) determines energy quantity stored in energy storage (7). A prognosticating unit (9) detects and displays an operating time of load based on the determined amount of power generation, stored energy and power consumption of load. A control unit (8) fixes the operating time based on the determined amount of stored energy so that the load is operated for fixed operating time. An independent claim is included for a method for operating power plant and energy storage.