New York Times

The first inklings of the idea came to Elon Musk and a cousin in an R.V. heading to the Burning Man festival in 2004.

Solar energy, they agreed, could be big.

But not even Mr. Musk, the billionaire behind the Tesla electric car, could have foreseen the solar power craze that is sweeping Wall Street. He and his cousins Peter and Lyndon Rive are riding a wave of exuberance over the industry and their young business, SolarCity.