What happened 

Shares of hydrogen fuel company Plug Power Inc (NASDAQ:PLUG) plunged 16.8% in November, according to data provided by S&P Global Market Intelligence, after reporting another big quarterly loss. 

So what 

Third quarter net revenue doubled to $35.4 million, but net loss more than tripled to $41.0 million, or $0.18 per share as the cost of stock warrants weighed on the company's financials. 

Hydrogen symbol made with leaves on a floor.

Image source: Getty Images.

What's worrying investors is that deals with Walmart and Amazon may weigh on results for the foreseeable future. Management said they need to maintain a high level of performance in the fourth quarter, which they said will be a high risk. 

Now what 

Plug Power doesn't have much room for error fulfilling its growing order book because its operating margins have been negative for a long time and management hasn't proven they can turn the trend around. If losses continue it'll force management to sell shares to fund operations, continuing a long-term trend of diluting shareholders. Until Plug Power turns operations around and starts making money I'll remain skeptical on this stock and investors should be cautious as well. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.