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What: Shares of thin-film solar manufacturer First Solar (NASDAQ:FSLR) saw its shares jump18% today after the company reported third-quarter earnings.

So what: Revenue was up 51% from a year ago, to $1.27 billion, and net income rose to $195.0 million, or $1.94 per share. Analysts were only expecting $1.00 per share in earnings, so the profit jump was quite a surprise.

Now what: First Solar's revenue and earnings can be lumpy, based on when projects are completed, and that's one of the reasons both revenue and earnings were up last quarter. The company sold three projects in Canada, and the new 550 MW Desert Sunlight project in California began to hit the books, boosting revenue and earnings. I'm encouraged by the improving margins, backlog, and increased earnings guidance of $4.25 to $4.50 per share, but I'm also worried that margins and revenue will fall going forward. Newer projects don't come with the same high margins as Desert Sunlight and, unless utilization picks up and costs fall, the company will struggle to grow revenue or earnings over the next few years.

Fool contributor Travis Hoium has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.