Credit: nationalgeographic.com

Helix Wind, a Vertical Axis Wind Turbine manufacturer, has had its assets bought by another VAWT company after it collapsed financially. While such turbines have a visual appeal and take up less space, making them ideal for rooftop installation, they are not as efficient as traditional horizontal axis turbines. Plus, decreased wind flow due to buildings being nearby cuts efficiency even more.

Critics of the design are blunt:

"Why do we keep repeating the same mistakes?" asked small wind turbine builder and author Ian Woofenden. "No vertical axis company has survived in the marketplace for any length of time. All long-term successful wind-electric manufacturers use horizontal axis designs. This is because they work."

Rooftop solar is more inherently practical than rooftop VAWTs. The real future of wind power is probably in gigantic offshore wind turbines, each of which can power thousands of homes.