Steve Dent for engadget:  A five kilowatt rooftop solar installation now costs just $12,500 on average after tax credits, and pretty soon, installing one might soon be a matter of re-tiling your roof. Whether it's right for you, however, depends in large part on how much sun your house gets. That's where Google's Project Sunroof comes in -- launched just two years ago, it has now surveyed over 60 million US buildings in 50 states. That means there's a good chance you can see the electricity production potential in your city, neighborhood and even specific house.

Google calculates the amount of sunlight on your roof based on "3D modeling of your roof and nearby trees," weather patterns, the position of the sun in the sky during the year and shade from buildings, trees and other obstructions. That info is then converted to energy production "using industry standard models for solar installation performance," Google says.  Cont'd...