Generac 6250 20,000 Watt Air-Cooled Aluminum Enclosure Liquid Propane/Natural Gas Powered Standby Generator without a Transfer Switch (Discontinued by Manufacturer) Unit runs on natural gas or liquid propane and features hands-free operation with no fueling, no manual start and no extension cords Clean, smooth True Power Technology provides safe operation of sensitive electronics Will require an automatic transfer switch 20,000 rated watts and this model is UL, CUL and EPA compliant for safety Comes with a 2-year limited warranty and is CARB Compliant