“Here there be photons”: Google’s Project Sunroof maps solar panel savings

This week, Google launched “Project Sunroof,” a side project that calculates a household's potential for solar panel output. People who live in Boston, the San Francisco Bay Area, and Fresno are invited to enter their address at the Project Sunroof landing page to see how much available sunlight their house enjoys and how much money they'd save if they installed solar panels in all of that available area.

Google says that to calculate all this information, it uses its aerial maps database, does 3D modeling of the rooftop, takes into account any shadows cast by trees or nearby structures, and then runs that against “all possible sun positions over the course of a year,” as well as “historical cloud and temperature patterns that might affect solar energy production.”

Once the numbers are calculated, you'll find out how much money you'll save if you leased solar panels for 20 years, used a loan to buy them, or bought them outright. Interested readers can use a slider to find out exactly how much of your roof you'd want to cover with solar panels in practice. “We recommend an installation that covers less than 100 percent of your electrical usage because, in most areas, there is little financial benefit to producing more power than you can consume,” Google writes.