What is Google Project Sunroof?


Aerial view of the Project Sunroof tool
Project Sunroof analyzes 3D heat map images provided by Google Earth. Image source: Techcrunch.com

Google has created software that can calculate potential solar savings based on your home’s roof shape and local weather patterns by utilizing machine learning and 3D models within Google Earth images. Essentially, Project Sunroof allows you to measure the benefits of rooftop solar for your home using Google Maps. 

Though similar to how the SolarReviews calculator works, Project Sunroof can’t analyze your solar savings or put you in touch with local solar companies to get your project started. Project Sunroof only gives you the option to measure different financing options to help you pay for solar, leaving you to find and vet potential installers on your own. 

In this blog, we’ll detail how Project Sunroof works, whether or not it is accurate, and what makes the SolarReviews calculator different when it comes to determining how much solar would cost you. 

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    How many solar panels would you need to offset 100% of your electric bill?

    How does Project Sunroof work, how accurate is it?

    In 2015, Project Sunroof was built by Google engineers, led by Carl Elkin, and uses an algorithm to compile data to give homeowners an estimate for their potential solar savings. Originally, Project Sunroof was only available in Boston, San Francisco, and Fresno but was then expanded to more U.S. states.  

    The goal of Project Sunroof is to provide solar installation data for customers to more easily learn about going solar. Project Sunroof works by gathering data on shade cover and rooftop images provided by Google, while Google factors in historical weather data and solar pricing from the National Renewable Energy Laboratory (NREL). 

    Clean Power Research provides utility ratings and solar incentives while information related to SRECS is pulled from Bloomberg. All of these sources are compiled based on a specific location to give a generalized estimate for a home. 

    You can enter your address and average monthly electricity cost on Project Sunroof to get an estimate of the potential size of a solar system your roof will need. But, it then brings you to Google to search for installers yourself instead of providing local options. 

    It also seems Project Sunroof is not the most reliable or accurate option because when I looked up towns across the U.S. the data provided was last updated in 2018. Project Sunroof is more of a cool side project for Google rather than part of its core business, so the information on Project Sunroof is not kept up to date or as accurate as it could be. 

    Project Sunroof used to formally sell leads to solar installer partners but eventually decided that it made more sense for them to stay out of that space and just operate as an option for people to learn about their home’s solar potential. 

    How does Google’s Project Sunroof compare to the SolarReviews calculator?

    The SolarReviews calculator tailors solar estimates based on your specific roof’s characteristics.  

    An alternative online tool option is the SolarReviews calculator. The SolarReviews calculator is more accurate because it is designed to measure factors that are unique to each individual roof. 

    SolarReviews does use technology from Project Sunroof to generate estimates, but it is more in-depth. SolarReviews tailors solar production measurements based on each roof’s pitch, shade cover, the amount of sunlight per roof, and direction. The calculator also incorporates utility rates charged by every American electric utility while making educated guesses about average electrical usage based on Energy Information Administration data

    While the Project Sunroof website does consider various factors, it usually recommends only a standard size solar installation instead of a tailored solar installation for your specific roof, like SolarReviews does. SolarReviews also connects you to local solar providers that will then give you an estimate based on local incentives and construction costs. 

    How much does solar cost?

    While solar energy costs vary based on your location and the size of the system that you will need, the average cost per watt of solar is $2.85 as of May 2021. This would make the average 6kW system cost $17,100. After the federal tax credit, the cost drops to $12,654. 

    However, that cost is the national average; solar power costs and solar energy potential could be better in your location. 

    By using the SolarReviews calculator, you can estimate the cost your specific roof would be and then opt to share that information with solar installers who can help you make the right choice for your size roof, the solar panels that make sense for you and your renewable energy goals. 

    Find out how much you can save by switching to solar

    Key takeaways

    • Project Sunroof provides information to prospective rooftop solar owners about potential savings and feasibility of going solar in their area.
    • Project Sunroof does not connect you to local solar installers like the SolarReviews calculator does.
    • The SolarReviews calculator is more accurate than Project Sunroof because it calculates data based on specific, individual roofs.
     - Author of Solar Reviews

    Ana Almerini

    Web Content Specialist

    Ana is a web content specialist at SolarReviews. She has 5 years of marketing experience blended with 2 years of experience in climate communications and holds a master of arts degree in climate and society from Columbia University. Ana frequently volunteers for environmental causes ranging from oyster reef restoration in NJ to expanding bike sharing in Naples, Italy.

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