Google can tell you if your home gets enough sunshine for solar panels

Using the same high-resolution aerial imagery that powers its online maps, Google on Monday introduced a new tool that lets Bay Area homeowners calculate the costs and benefits of installing rooftop solar panels.

Typing a home address into Google’s new Project Sunroof website sends a user to a bird’s-eye neighborhood view, with roofs color-coded in a range from sun-drenched yellow to shady purple. The tool calculates how much money a resident would save with a solar rooftop, then directs the user to companies that can install the panels.

Along with pushing Americans to adopt cleaner energy practices, Google will eventually make money from the new product with a commission for each Web referral to a solar energy provider.

“I learned that many people are in favor of going solar … but they wrongly believe it’s very expensive,” said Carl Elkin, the software engineer who created the new tool, in an interview Monday.

A self-described solar geek, Elkin began developing the tool as part of the company’s “20 percent project” in which employees are encouraged to spend a portion of their work time on ideas that inspire them. He is now working full-time on Project Sunroof from the company’s branch office in Cambridge, Mass.

“I knew in principle that solar is very cheap and has been for some time, but when you see the sheer scale of how well it can work, it really is quite amazing,” he said. “One begins to wonder, ‘What’s holding people back?’ We believe it’s because people don’t realize how cheap it is.”

The pilot tool only works in three regions so far — the Bay Area, Fresno and greater Boston — but the company intends to expand around the country and world. In the Bay Area, it now covers most of the residential South Bay, East Bay, Peninsula and Marin County, but not Sonoma, Napa, Solano or Santa Cruz counties.

The tool works using a combination of data already collected by Google, which is now a subsidiary of parent company Alphabet. The analysis counts hours of usable sunlight per year based on day-to-day neighborhood weather patterns. It also shows the estimated square footage available for solar panels based on a 3-D modeling of a home’s roof and nearby trees or high-rise buildings using imagery collected by aircraft for Google Earth.

Then, it considers local electricity rates and solar incentives to compute an estimate for net savings with a 20-year solar energy lease.

Glancing through suburban Bay Area neighborhoods with the tool displays roofs that appear more solar-friendly than in greater Boston because of New England’s cloudier weather patterns and denser tree canopies. But for many homes, the estimated savings calculated through the tool ends up the same or better in Boston because of local government incentives that reward homeowners for installing solar panels.

The tool directs Bay Area home or building owners to five solar companies that can be hired to install panels: San Jose-based SunPower, Belmont-based SunEdison, Milpitas-based nonprofit SunWork Renewable Energy Projects, as well as Texas-based NRG Energy’s Home Solar program and Utah-based Vivint Solar.

Notably absent from the list is Elon Musk’s San Mateo-based SolarCity, which has obtained financing from Google but already uses software and aerial images to estimate price. Such software tools have been around for years — Oakland-based Sungevity launched an internal tool in 2008, and the National Renewable Energy Laboratory runs a public one called the PVWatts Calculator — but Google’s tool is immediately accessible and has a fancier interface.

Google is in discussions with other providers to join the network as the pilot project gets user-tested and expands, said Joel Conkling, the business lead for Project Sunroof, who declined to name any specific companies.

A Massachusetts company that runs its own solar estimate tool said one of Project Sunroof’s biggest shortcomings is not finding a way for a true shopping experience that allows users to compare and contrast multiple installation quotes.

“Because Google lacks a solar marketplace full of real-time pricing data, it’s unclear where their installation price estimates actually come from,” wrote EnergySage CEO Vikram Aggarwal in an email Monday. “The tool suggests several installers that could be contacted to take on the installation project, but it provides homeowners with virtually no information about that installer’s brand, track record, or quality. Analogous to paying for a spot atop Google’s search engine, solar installers simply pay Google to participate.”

Update 8/18/2015: I’ve got a lot of emails today about places Project Sunroof doesn’t yet reach. It covers much of the inner Bay Area but not all of it. For instance, it covers the inner East Bay, but doesn’t reach as far east as Antioch or Brentwood.

Above: Screenshot of Google’s new Project Sunroof tool, as used for the sun-drenched roof of a suburban house in southwest San Jose.

 

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