As we reported a few months ago, SolarCity is planning an initial public offering (IPO, which means to become a public company with shares being traded on a stock exchange). This could happen soon, as the company has submitted a draft registration statement to the Securities & Exchange Commission on April 26th.
SolarCity is definitely going against the clean energy crowd: "SolarCity is seeking to go public while other renewable- energy companies are abandoning their IPO plans. BrightSource Energy Inc. (BRSE), a developer of solar-thermal power plants, and the cellulosic ethanol producer Enerkem Inc. both withdrew their registrations this month."
The registration documents don't mention the expected market cap, but previous estimates have been around $1.5 billion.
SolarCity is now the top solar installer in the U.S., and an IPO could help it grow some more by giving it access to the capital markets. We don't know yet how profitable they are (we'll find that out when the IPO papers are filed), but they have powerful partners (such as Google, which financed $280m of residential solar installations) and that "think big" startup spirit.