Project Sunroof uses information in Google Maps to figure out how much sun falls on a roof and takes into account stuff like the angle of the roof, the weather, and obstructions like trees and chimneys.

It then uses those measurements to figure out how many panels you’d probably need and how much you could save on your electric bill, including solar incentives in your area. You can also see how buying or leasing panels affects your savings, and then send your estimate to installers in your area, instantly.

Project Sunroof currently only works in Boston, the San Francisco Bay Area, and Fresno. But anyone can sign up to find out when it expands to their neighborhood.