This week on Watt It Takes: How a Texas entrepreneur with fossil fuel roots came to see solar and storage as the future of energy. We feature a conversation with John Berger, the CEO of the residential solar-and-storage firm Sunnova, about his mission to convince traditional energy investors to put their money into solar. Sunnova has pulled in tens of millions of dollars from investors who once thought solar was laughable. "I'm proud of getting a bunch of oil and gas money. I worked hard to get that money. And I want a lot more of it.