Solar energy continues to progress by leaps and bounds in the United States; in 2016, residential solar installations nearly doubled nationwide, and this was accompanied by a record-breaking expansion of the utility-scale sector. But for every homeowner or business making the leap to solar, there are many others out there who have yet to tap into this resource. Many reasons explain their reluctance, but one key obstacle is uncertainty: they aren't sure if their roofs are good candidates for solar panels, they don’t realize how much they could potentially save, and they don’t know how they could finance a solar installation.

Manhattan as seen by Google's Project Sunroof (screenshot courtesy of Google)

Free software developed by Google addresses this uncertainty, and could therefore help unlock large-scale solar energy usage in the United States. Project Sunroof, launched back in 2015, aims to show which houses have roofs that are viable candidates for solar panels. Though the project started off small, it has now expanded to every state, and includes 60 million rooftops across the country in its database.

Project Sunroof uses data and images from Google Earth and Maps, along with some data-crunching engines, to generate graphics that display the average amount of sunlight hitting each portion of a roof. In its calculations, Google takes into account local weather patterns, the position of the sun, and shade-generating factors such as trees or nearby buildings. The resulting image looks like a thermal scan, and uses cool purples to illustrate shaded areas, and pale yellows to show portions of the roof receiving light. The company claims that overall, 79 percent of the rooftops analyzed using Project Sunroof are viable locations for solar panels.

Households entering their average electricity bill into the program receive an estimate of the money they would save by installing solar panels, as well as the area of the roof that would need to be covered in order to fulfill 99 percent of their electricity needs. The site also recommends various financing options available to individuals, including leases, loans, and outright purchasing.

Project manager Joel Conkling says that the purpose of Project Sunroof is “to get data into the hands of people thinking about solar, and who are making decisions about solar.” The hope is that by providing this information easily and for free, more people will be enticed into making the commitment, once they see whether it is an economically viable option.

The solar potential of a roof is just one part of the equation when it comes to convincing customers to consider solar; consumers are also influenced by state renewable energy targets, metering rates, the availability of subsidies like tax credits, and other financing options. Though it is certainly not comprehensive, Project Sunroof can provide a snapshot that helps consumers match their price point with their financing options. It can also provide useful data to solar installation companies about which areas have high solar potential, making them good targets for advertisements.

Graphic by Emma Dietz, source data from Google

The program also provides critical big-picture data, especially in terms of quantifying the overall rooftop solar potential in the United States. According to the Energy Information Administration (EIA), the average U.S. home uses 10,812 kilowatt-hours (kWh) of power each year. This means that one gigawatt-hour (GWh) is enough energy to power approximately 90 homes for one year. The city with the highest solar roof potential, as determined by Project Sunroof, is Houston, Texas; Project Sunroof estimates that rooftop solar could generate a whopping 18,940 GWh per year from Houston if the city used solar panels to the fullest extent. That's enough to power 1.7 million homes (there are 1.4 million houses in Houston, according to the U.S. Census). If the cities with the top ten greatest solar energy potential maximized their output, they would collectively produce enough energy to power 8 million homes across the United States. That’s a lot of power!

You can visit the Project Sunroof website, enter your address, and explore the solar potential of your own home. The site will provide you with a savings estimate based on your current electric bill, financing options based on the results of your home, and a list of local solar installers whom you can contact if solar energy seems right for you.


Author: Emma Dietz