Does it make sense to install solar panels on your roof? You probably have no idea. But as of today, Google knows. The colorful and recently alphabetized search monstrosity has launched a new tool called Project Sunroof. It will use data you may not have realized that Google even had to tell you how much money you can save by turning your roof into a photon harvester.
For my girlfriend’s old house in Menlo Park, Calif., Google says she could have saved $600 a year by installing enough photovoltaic panels (25 square meters) to generate 4 kilowatts. Installation would have cost her a total of $0 on a 20 year lease. Google calculates the amount saved by taking into account typical utility rates, relevant federal and state tax credits, utility rebates, and whatever renewable energy credits might be available in your area. Meanwhile, the power that the panels can theoretically produce is modified by what Google knows about local weather patterns on a day-to-day basis.
It’s not as though calculators like these didn’t already exist: the U.S. Government’s National Renewable Energy Laboratory has one called PVPWatts. All you need to know to use it (besides your address) are things like DC system size, module type, array type, expected system losses, and the tilt and azimuth of your roof. And some other stuff. Finding this information isn't even that difficult if you want to put the time into it (and you have a way to access your roof without killing yourself). Google’s calculator will keep you off your rooftop because it has done most of the hard work for you. You need to know nothing besides your address and the amount of your typical monthly electric bill.
Most significantly, Google is able to estimate not only the size of your roof, but also its orientation and slope and whether trees or other buildings may block the sun at certain times during the day. Google hasn't provided any details on how this all works, but we can guess: By now, Google has access to enough aerial imagery that it can generate 3-D models of buildings and trees using oblique images taken from different angles. While it seems that direct access to the 45 degree image sets is no longer available, here are some examples of 3D models created from them. Google hasn't 3D-ified the entire United States yet—which is at least in part why Sunroof is currently restricted to just a few cities: the San Francisco Bay Area, Boston, and Fresno.
This tool is certainly valuable for anyone thinking about a solar panel installation, and for anyone who wants to know whether he or she should be thinking about it. It’s a potentially valuable tool for Google as well, since those suggestions for companies to install solar panels for you are sponsored by the companies themselves. In other words, Google is giving you unbiased information about whether you might want solar panels installed, and then (potentially) biased information about who should install them, since you may not see companies on that list if they haven’t paid Google for the privilege.
We can’t really fault Google for this. It deserves to make money off of a useful service that it has created (or at least refined). Our recommendation, though, would be to use this tool to find out whether solar power is right for you, and then consider using Google the old fashioned way to find the right company to make it happen.