The invention relates to a system for improving the energy efficiency in hydraulic systems, comprising an actuator (49) which, in an operating state, operates as a consumer of hydraulic energy and, in a different operating state, as a generator of hydraulic energy, and a hydraulic accumulator (1) which, when in an operating state of the actuator (49), can be charged by the same for storing energy and, when in a different operating state, can be discharged for delivering energy to the actuator (49). The invention is characterized in that at least one hydraulic accumulator in the form of an adjustable hydropneumatic piston accumulator (1) is provided, in which a are formed a plurality of pressure chambers (19, 21, 23, 25) which adjoin effective surfaces (11, 13, 15, 17) of different sizes on the fluid side of the accumulator piston (5), and an adjusting arrangement (51) is provided which connects a selected pressure chamber (19, 21, 23, 25) or a plurality of selected pressure chambers (19, 21, 23, 25) of the piston accumulator (1) to the actuator (49) as a function of the pressure level that prevails respectively on the gas side of the piston accumulator (1) and on the actuator (49).