Elon Musk, chairman of SolarCity and CEO of Tesla Motors, speaks Oct. 2, 2015, at SolarCity's Inside Energy Summit in  New York. Among SolarCity, Tesla, and SpaceX, Elon Musk's interests got at least $4.9 billion in taxpayer subsidies over the past 10 years. (Photo: Rashid Umar Abbasi/Reuters/Newscom)