In order to do this, Project Sunroof is attempting to take a lot of the guesswork out of solar panel installation. By simply putting in your address, Google then will find your home on Google maps and combine that with weather and solar data for your rooftop.
From this information, Google can then approximate how much solar energy your rooftop panels might generate given how much sun your roof gets in a calendar year. The system will then approximate how many solar panels you might use and calculate the savings you would receive by switching to solar. Finally, it would then put you in contact with solar panel providers in your area so that you can take steps to getting solar installed.
You may have to wait awhile to try out Project Solar as it is currently only servicing Boston, San Francisco and Fresno. You can check out their launch video for more information here.