The immediate goal here is vertical integration. The company, which was co-founded by Tesla CEO Elon Musk, wants to handle all aspects of the solar supply chain, from design to manufacturing to sales to installation. It's basically the Apple model — only for solar panels.

But SolarCity's ultimate aspiration is to drive down prices dramatically. In a call on Tuesday, Musk said that the aim was "to have solar power compete on an unsubsidized basis with fossil-fuel energy from the grid." (The company was also founded by brothers Lyndon and Peter Rive, who currently run it.)

Is that doable? SolarCity has had success with its current business model — offering rooftop solar systems at no upfront cost to customers who make monthly payments spread out over many years. The company now handles 25 percent of all US residential solar installations — and is aiming for 1 million customers by 2018. This latest move means SolarCity will be able to produce its own panels for these systems and try to lower its costs even further.