The installed power of the pump and turbine assembly is arbitrary, determined only by the intended field of application. Standard pumps function using a predefined power capacity. At their optimum operating point the power consumption and water flow are constant. Standard turbines, however, can be adjusted to the required power by regulating the water flow. When the pumps and turbines are simultaneously active a portion of the water is circulated (hydraulic short circuit), thus creating an infinitely variable energy output or consumption possibility at any time, while still operating at optimum efficiency. Furthermore, changing the operating status of pump to turbine mode and vice versa (special uses with rapid load changes) can be done very quickly.