Google has got a good look at your roof, and can tell you if it is worth the investment to install solar energy panels.

The US tech giant said its "Project Sunroof" online tool is now available in the area around San Francisco and Fresno in California and around Boston, Massachusetts.

The new tool "uses high-resolution aerial mapping (the same used by Google Earth) to help you calculate your roof's solar energy potential, without having to climb up any ladders," Google engineer Carl Elkin said in a blog post.

The website "figures out how much sunlight hits your rooftop throughout the year, taking into account factors like roof orientation, shade from trees and nearby buildings, and local weather patterns" and then "combines all this information to estimate the amount you could potentially save with solar panels," Elkin said.

It can also connect homeowners with local solar providers.

Elkin said the effort aims to overcome consumer concerns and encourage the use of green energy that reduces carbon emissions.

"The cost of solar power is at a record low," he said.

"A typical solar home can save hundreds or even thousands of dollars per year on their electricity bill.

"But, as a volunteer with the Boston-based solar program Solarize Massachusetts and a solar homeowner myself, I've always been surprised at how many people I encounter who think that 'my roof isn't sunny enough for solar,' or 'solar is just too expensive.'"

Google hopes to expand the project to additional regions "in the coming months," Elkin said.

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