google project sunroof

Google Project Sunroof: making solar easier

The cost to install solar has dropped by more than 70 percent in the last decade, with prices in Q3 of 2020 hitting the lowest levels ever recorded. Yet many still believe that solar is only a luxury item for green-minded consumers, rather than a long term cost-saving investment. Why is this? A big reason is the lack of easily accessible information about how solar can save you money. Like EnergySage, Google’s Project Sunroof looks to fix this using smart technology.

Key takeaways

  • Google Project Sunroof is a solar calculator tool that helps the public educate themselves on their solar opportunities with the ultimate goal of making solar more accessible
  • As of late 2020, Project Sunroof has reached more than 60 million roofs across all 50 states
  • The EnergySage Marketplace will take into account alternatives to rooftop solar like ground mount or community solar, whereas Google Project Sunroof will not. 

What’s in this article?

What is Project Sunroof?

Google Project Sunroof is an initiative started by Carl Elkin, a Google engineer in Cambridge, MA. Originally a 20% project, Elkin’s online tool went live in 2015 to help homeowners determine if their home is ideal for solar energy and if the potential savings are worth the investment. Project Sunroof’s biggest claim to fame is its solar calculator tool, which uses multiple data sources to determine how much a home would benefit from a rooftop solar system. 

The imagery provided by Google Earth allows for the creation of a digital surface model, which shows the direction that the roof faces (south or southwest exposure is best), the angle of its tilt, and the presence of shading objects like trees. With that information, Google models how much sunlight hits the roof over the course of the day using 3-D geometry. By adding in data about local weather patterns from the National Renewable Energy Laboratory (NREL), and taking averages over the course of a year, Project Sunroof can provide a solid baseline estimate of a roof’s solar potential. 

From here, it only requires a few more calculations to give a custom cost estimate for any home. Simply enter your address to give it a try here

What problem does Project Sunroof solve?

Like EnergySage, Project Sunroof seeks to solve the problem of information transparency in the solar industry. For many people, going solar is a challenging process that’s filled with research and questions. There is no shortage of solar information and data on the Internet, but it is extremely dispersed, and sometimes difficult to understand for those unfamiliar with the industry and its terminology. 

Project Sunroof seeks to make going solar easier by providing the public with accurate, fast, and easy to understand data. All you need to do is enter in your address, and Google does the hard work behind the scenes, providing you with an accurate estimate of how much you could save with solar. They pair this with a “heat map” visual of your roof, giving a clear picture of its solar potential. Lighter colors represent sunnier areas, and darker tones indicate shading.

google project sunroof

What are the drawbacks of Project Sunroof?

At this time, Project Sunroof has not reached every roof in the United States. Although Google continues to add new properties every day, the service is not yet available for every home. However, as of late 2020, Project Sunroof has reached more than 60 million roofs across all 50 states, so there’s a good chance that your home has been mapped already! This should continue to improve as Project Sunroof expands its coverage in the coming months and years. 

How accurate is Project Sunroof?

While Project Sunroof may not have been as accurate in 2015, updated algorithms over time improved the accuracy of the online tool. According to Project Sunroof’s changelog, it hasn’t been updated since 2018, so that may no longer be the case. Some of the data may be outdated due to new solar energy incentives or other changes.

Project Sunroof also doesn’t consider alternatives to rooftop solar systems. For properties with a large sunny area, such as a field, ground-mounted solar panels may be an option. These systems may offer more flexibility, such as adjusting the angle of solar panels, than what is typically available with rooftop solar. 

That being said, there are numerous factors that go into a solar calculator, and while calculators are good for providing general guidance, a professional, NABCEP-certified solar provider – like those on the EnergySage Marketplace – can provide a more accurate estimate based on your rooftop orientation and angle, in addition to other factors. 

Project Sunroof vs. EnergySage’s Solar Calculator: What’s the difference?

Because EnergySage has our own Solar Calculator, we often get questions about how our tool differs from Project Sunroof’s – truthfully, we use Project Sunroof’s data directly to help create our own savings calculation! Their data mapping capabilities combined with numbers straight from custom solar quotes in our Marketplace allow us to create the most accurate solar cost and savings estimates possible.

It works like this: Project Sunroof tells us how much sunlight hits each part of your roof over the course of a year. We then use this data to predict how much energy an average solar panel would generate on your roof. Once we have this number, we use your electricity bill and roof map to estimate how much electricity an array of solar panels could produce for your property. This, coupled with our Marketplace cost data for solar in your area, gives an accurate estimate of how much money you could save. 

The EnergySage Solar Calculator has a couple more benefits over Project Sunroof. Firstly, even if Project Sunroof has not mapped your roof yet, we can still provide you with an estimate of your solar savings! In these scenarios, we assume 100 percent bill coverage from solar, calculate how much you would save based on solar prices and electricity rates in your area, and then add a note of how many square feet of your roof you would need to fit those solar panels. 

Second, we also show savings estimates for community solar alongside rooftop financing options in states where this is available. This can be especially helpful if you can’t install solar panels on your roof, but still want to take advantage of solar power.

How does a Sun Number estimate your solar suitability?

Project Sunroof uses a gradient to determine how much sunlight a rooftop receives, with purple indicating intense shade. The gradient transitions from purple or orange to white, indicating full sunlight. 

Other solar calculators use a Sun Number, or sun score, to determine how suitable a property is for solar. A numerical score from 0 to 100, this score isn’t just based on how much sun or shade a rooftop has, but also other factors like climate, the building, and the average energy needs of homes in the area to determine potential solar savings. 

Can’t install solar panels on your roof? Consider community solar.

If community solar is available in your state, you can get a quick savings estimate using our Solar Calculator. Plus, our Community Solar Marketplace allows you to search open projects by zip code – take a look today to see local community solar options, or sign up to receive updates as new projects open up in your area! Community solar is not only beneficial for homeowners, but renters can sign up too to save on their monthly electricity bill.  

Frequently asked questions about and related to Project Sunroof

How does Project Sunroof work?

Project Sunroof utilizes Google Earth’s imagery to create a digital model that looks at the direction a roof is facing, the angle of the roof, and shade factors to determine how effective a rooftop solar system would be.

How accurate is Project Sunroof?

Because a solar calculator cannot substitute a quote from a certified solar provider, consumers can expect a Project Sunroof estimate to be as much as 20% higher or lower than the actual cost of a solar system.

What is a good Sun Number?

A score of 70 or more is generally considered a good Sun Number. A score below 70 simply means that a home isn’t ideal for solar; homeowners with a lower score may still see a benefit from installing solar panels.

Is my house good for solar according to Google?

Several factors go into determining if a home is suitable for solar. We recommend exploring the Project Sunroof tool to see if your address is covered and, if so, what Project Sunroof’s analysis indicates.

Explore your solar savings with EnergySage’s calculator today!

Get the best data from both Project Sunroof and EnergySage and explore your cost savings with the EnergySage Solar Calculator. We use the most accurate information available to give you a strong estimate of how much you’ll save by going solar. If you’d like to take advantage of these potential savings, create an account with us, and we’ll provide you with competitive quotes from local installers!

3 thoughts on “Google Project Sunroof: making solar easier

  1. Robert Baker

    Your calculator is off…dramatically so. It seems to use the roof area of both my home and my neighbor’s in it’s calculation ( homes are duets). Therefore the information provided is useless!

  2. Dan E Muller

    Sir yes, solar is looking very attractive. Growing up on a farm in Idaho I have always been sort of self sustained.
    Looking forward to your reviews like a dog waiting for a bone but I still have doubts that my master will ever throw the bone. The two biggest problems I will ask about and the many subproblems will have to wait.
    One I am retired living on SSI ,so I pay no income tax do not even file a 1040. As I review your calculations on the cost and payback of solar they almost always include a Tax incentive from the Government. My question is are there any incentives old retired famers? Or rebates from somewhere else?
    The other is that I am sort of a DIY person. For the last 3 years I have got some quotes to install a new heating and cooling system in my home. The quotes were all around $10,000. The represents that came out wanted seemed to analyze exactly what would be needed. Therefore I concluded that what they had in mind was a rip off. I have since bought a Goodman 3 ton heat pump system complete and installed it for less than half that.
    So that brings up the people in solar system business. I know everyone needs to make a business work, but for a DIY no ones seems to have the time for the simple talk, especially when such talk will cause the customer to buy someplace else.
    I am thinking in terms of buying used panels then having to buy mounting brackets for them. Then of course the controller, the inverter, the wires, and the storage system, if I were to buy all those used it in not likely I would get much help. I do understand their problems with that. But for years and year farming and the cattle business could ask many local dealers, vets, lumber yard, vets and many businesses in evolved and they would help. Not so with the HVAC business while your solar blog is good, I think when you get down to some old farmer asking how do thing he knows very little about I would not get much help.
    Dan Muller


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