We recently explained how Tesla needs to build what it is calling a "gigafactory" for batteries in order to survive. The rest of the world is not building enough lithium ion storage to meet what Tesla thinks will be surging demand, so it has decided it must do it itself by making a very costly factory.

Tuesday, SolarCity (Elon Musk's other company) announced it will have to do the same for solar panels. The firm unveiled plans to build one of the world's largest high-efficiency solar panel plants, using technology from Fremont-based Silevo, which they also said they'd acquired.

"We expect to have to install 10 gigawatts [of high-efficiency panels] a year," Chairman Elon Musk said on a conference call announcing the move. "If you look at the current capacity in the world, we're not able to do that right now."

It's not just a supply question. Solar panel prices have been falling in recent years thanks to a production boom in China. But the panels getting produced, though cheap, aren't terribly efficient and prices have begun bottoming out anyway.

They are likely to begin climbing: Government subsidies for renewables start getting phased out in 2016, and the political environment for rebooting them remains unstable at best.

Plus, in a call with BI, CTO Peter Rive said recent U.S. moves to slap tariffs on Chinese panels served as a "catalyst" for looking into building the Silevo plant.

Will the demand be there? The firm's own polling suggests there is. But if you assume that electricity customers are price agnostic, rooftop solar still has some ways yet to go to become cost competitive with fossil fuels. Musk recognizes this and beating fossil fuels at their own cost game remains his ultimate goal. As of last year, the levelized cost of energy for rooftop generation remained about double coal.

Lazard



Goldman has explained that it still very much believes in SolarCity. Its systems have a great shot at getting to parity as long as storage costs come down. But as Goldman and Barclays have said, storage costs will come down only if the real gigafactory, Tesla's, can take off.

Musk did not rule out selling their new panel technology to others. Utility-scale solar remains the largest source of solar generation in the U.S., and there is no sign they've made any moves to confront the coming price hike. Utility developers wouldn't be in a position to do much any way.

So SolarCity, and the solar industry at large, sure looks like it needs these two gigafactories to continue to thrive.