First Solar (FSLR 0.99%) is maybe the most puzzling company in solar, once a dominant force but now an afterthought for investors. Still, it's one of the most profitable companies in the industry, and with earnings expected at $2.40 to $2.80 per share that will continue this year. 

But that doesn't mean that there aren't challenges ahead. First Solar's panels are still less efficient than those of the competition, and that will have to improve for the company to stay competitive long-term. Then there's the falling cost of solar systems, which is resulting in lower margins, in part because of those inefficient panels. 

Solar specialist Travis Hoium takes a look at First Solar's position and whether or not this is a stock investors should be buying today.