The Endurance S-250 wind turbine can be connected directly to the power grid without the need for an inverter. It has a power rating of 5 kWh and can match the energy requirements of average U.S. households that consume up to 18,000 kWh per year, the company says. A braking system and over-speed protection stop the rotors in cases of extreme high wind or fault conditions. 888.440.4451. www.endurancewindpower.com.