A combination door operator assembly and door, wherein the door operator assembly includes an operator unit mounted to the door on the pushing side thereof, an arm linkage having a driving arm and a driven arm, a mounting bracket on the frame of the door, a rechargeable power storage pack having at least one of a rechargeable battery and one or more capacitors, and a controller for monitoring a speed and a position of the door, wherein when the door moves faster than a predetermined speed, the motor is used as a generator to charge the rechargeable power storage pack and the speed of the door is reduced.