What: Shares of Plug Power Inc (NASDAQ:PLUG) dropped as much as 15% today after the company released second-quarter earnings.

So what: Quarterly revenue was up 39% to $24.0 million, but the company swung from a profit of $3.8 million a year ago to a $9.3 million loss. On an adjusted basis, the company lost $0.06 per share, which was a penny better than expectations. The problem is that analysts expected $25.2 million in revenue, and for a company with high growth goals, that's a problem for Plug Power. 

Now what: Even a hint of slower-than-expected growth can lead a stock like Plug Power to sink, and that's what we're seeing today. But I actually see some positive signs in the results. Product gross margin improved from 17% a year ago to 24%, and total gross margin was up from 1% to 7% over the same time. That hasn't led to a profit yet, but it's progress for a growing company.

I'd like to see more financial progress and even a profit before jumping in, but long-term investors should like what they're seeing operationally, and the falling stock price could make this a good value for investors someday.