On the fringes of green technology

If you had a problem with your neighbor putting up a DirecTV dish on his house, just think how you will feel when he erects a Windspire turbine from Mariah Power. Actually, maybe not that bad. The 30-foot wind turbine is planted vertically on commercial buildings but horizontally on residences, so you don't see it. (In the horizontal position, wind bouncing off the roof can drive the turbine, says CEO Mike Hess.) The Windspire costs about $5,000 and cranks out a kilowatt of power, enough for a small home or a third of the power for a McMansion. Mariah as 1,500 units on order.

AeroVironment, meanwhile, has Flying Monkey-like turbines for commercial buildings.

Wind, unfortunately, remains the most difficult renewable energy source to predict. Consumers thus may worry about getting their money's worth.