"Our intent is to combine what we believe is fundamentally the best photovoltaic technology with massive economies of scale to achieve a breakthrough in the cost of solar power," Musk, SolarCity's chairman, and company co-founders Lyndon and Peter Rive wrote in a blog post.

"Goal is for unsubsidized solar power to cost less than grid electricity from coal or fracked gas," Musk said in a tweet Tuesday morning.

What we are trying to address is not the lay of the land today, where there are indeed too many suppliers, most of whom are producing relatively low photonic efficiency solar cells at uncompelling costs, but how we see the future developing," the company's blog post read. "Without decisive action to lay the groundwork today, the massive volume of affordable, high efficiency panels needed for unsubsidized solar power to outcompete fossil fuel grid power simply will not be there when it is needed."

"Thanks to the economies of scale that will come from Tesla's gigafactory, within 10 years every solar system that SolarCity sells will come with a battery-storage system, says Mr. Rive, and it will still produce energy cheaper than what is available from the local utility company."