A combination door operator assembly and door, wherein the door operator assembly includes an operator unit mounted to the door on the pulling side or the pushing side thereof, an arm linkage having a driving arm and a driven arm, a mounting bracket preferably mounted on the frame to which the door is hinged, 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.