A power boost assembly is disclosed that can be used with a door actuator, such as a door closer. The power boost assembly is structured to store an energy during a first movement of a door and release the stored energy during a second movement of the door. In one form the power boost assembly can be structured as a module that can be added to an existing door and door closer installation. In one form the power boost assembly is used to increase a closing force imparted to a door to ensure a latching event.