Chamberlain. The only screw-drive unit in the maker’s Elite Series product line, the LiftMaster Elite Model 3840 is a 13/4-horsepower DC motor screw drive garage door opener, and features EverCharge Standby Power, which continues to power the unit for up to 40 cycles during an outage. Other features include 200-watt lighting, programmable door travel and force settings, and a Smart Control Panel that informs users of the time, the garage’s temperature, and status messages regarding opener maintenance. 800.528.6563.