Google Solar Map

Google has released a updated “Project Sunroof”, which is a more complete estimate of solar power potential for roofs throughout the US.

In one sense, this is scarcely news, since the basic technology has been around for decades. (For that matter, the trees in my neighborhood make the answer pretty obvious without any complicated math: nice shady yard == poor solar energy potential.)

The news is that Google has done the job in bulk, using their dragon’s horde of information and computational resources.

Project Sunroof calculates the amount of sunlight received by each portion of the roof over the course of a year, taking into account weather patterns, position of the sun in the sky at different times of year, and shade from nearby obstructions like trees and tall buildings.

This data is projected into Google Maps, so you can look up your own house, or whatever you are interested in.

The other thing Google has done is to work up some larger scale statistics, suggesting the potential solar energy for cities and states.

As an old solar enthusiast, this is pretty neat, and might inspire people to think about adding rooftop solar.

I have a few caveats, though.

First, this dataset is based on a snapshot, and conditions might change. Ten years ago, my house was even shadier than it is today, until a large tree died. But on the other side of the house, another tree has matured to full size, increasing shade on that side.

Note, too, that tall buildings spring up all the time, shading swaths of their neighbors. And, for that matter, old houses are renovated or torn down.

In other words, whatever the solar potential today, things will change over the lifetime of the solar installation (decades).

Another point is that the solar potential is only the foundation. You need to know the costs of retrofitting, which are far from trivial in older buildings. For instance, you might need significant upgrades to the wiring and roof.

A third point is, of course, storage or grid connection. Are you going to store the energy on site? How? Or do you want to connect to the Grid as a nano generator? If so, can you actually do that in your area? (Hint: if you have a Republican state government, the answer is trending toward, “no”.)

Still, have a peek and see the bright orange high potential spots, and then look for local sources (e.g., Solar Urbana)


  1. Joel Conkling, Shedding light on solar potential in all 50 U.S. States, in The Keywork. 2017, Google. https://blog.google/products/maps/shedding-light-solar-potential-all-50-us-states/
  2. Google Maps. Project Sunroof. 2017, https://www.google.com/get/sunroof – p=0.

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