A new method of measuring the torque and speed of three-phase motors enables reliable, economical and accurate power input measurement in pump systems. The operating costs of pump systems can thus be effectively reduced. This has been confirmed by the measurements at the Gemeinschaftskraftwerk Linden (GKL) of the Stadtwerke Hannover AG (Communal Power Station of the Hanover Municipal Works). With this method, the power input at the pump shaft is much more transparently and sensitively determined than by the still very frequently used method of calculating the power from the current consumption of the motor.