Ed Lenz's house is pretty hard to miss-it's the one with a home-built vertical-axis wind turbine on the roof. A career tinkerer, Lenz put the turbine up there for a test run three years ago, and it's still turning away today, a super-quiet model of efficiency and ingenuity. The "Lenz2" turbine, built primarily from easy-to-find supplies like aluminum, plywood and magnets, can produce about 50 kilowatt-hours of electricity per month with steady wind. Its output-about 10 percent of the total power Lenz uses-is then stored in a battery bank that feeds into his home lines. The slow-turning vertical-axis design is most efficient in gusts of 6 to 20 mph, so it's ideal for relatively low-wind areas like western Michigan, where he lives. You can download plans at windstuffnow.com to build your own Lenz2. It's not a quick weekend project, but once it's up and running, paying the electric bill should be a breeze.