Primus Wind Power is proud to present the Air 40 Wind Turbine. It is so quiet that you almost can't hear it! Primus wind turbines are the only small wind turbines made in the U.S.A. for marine and small residential use. High quality construction makes for good longevity. Overspeed protection (braking) in high winds allows for turbine protection. A microprocessor regulates and controls charging for perfect performance. Don't let size fool you. With a low startup speed of 7 mph, it regularly delivers more overall power per month than larger turbines with 400 watts. Comes with a 5 year warranty.