A device and a method for operating multiple centrifugal pumps are disclosed. The device can include a communication interface for receiving as at least one input information, an instantaneous pressure drop and an instantaneous flow rate per pump or speed of the centrifugal pumps, and for transmitting output information to the centrifugal pumps, where the output information reflects a reference value for the number of centrifugal pumps to be operated in parallel. The device can contain a data storage unit and a processing unit, which determine from input information and additional information an instantaneous efficiency, a first expected efficiency under the assumption that the actual number is reduced by one, and a second expected efficiency under the assumption that the actual number is increased by one, and which can generate the reference value depending on which of the instantaneous or first expected or second expected efficiencies has a highest value.