A system having a variable diameter impeller device that is operable for reducing an energy consumption of a rotating fluid or gas pump by increasing the impeller diameter as a speed of the rotating fluid or gas pump increases and decreasing the impeller diameter as the speed decreases. An extendable vane arrangement is configured to move along an elongated curved or sloping slot, the movement along the elongated curved or sloping slot is operable for increasing and decreasing a diameter of the impeller device. A spring arrangement having a first end and a second end extends and retracts to dynamically increase or decrease a diameter of the impeller device.