It may not surprise many that in sunny California rooftop solar energy is more common than anywhere in the United States. This month, by a 5-0 vote, California’s Energy Commission made solar mandatory for most new homes and apartment buildings starting in 2020.

We get the story from Dan Gearino, a writer for Inside Climate News. His latest article is, “In a First, California Requires Solar Panels for New Homes. Will Other States Follow?” Illinois is one of the more aggressive states in pursuing sustainable and renewable energy. We talk with Nate Kipnis, founder and principal of the Evanston-based firm Kipnis Architecture and Planning. He tells us what would it take to make such a law happen in Illinois.