What happened

Shares of hydrogen fuel cell pioneers Plug Power (NASDAQ:PLUG) and FuelCell Energy (NASDAQ:FCEL) exploded higher in Wednesday trading, rising 5.4% and 9.8%, respectively, by noon. Tagging along for the ride (and even exceeding those stocks' gains) is a fast-growing battery maker, Flux Power Holdings (NASDAQ:FLUX), which notched an 11.5% gain.

So what

There doesn't seem to be any obvious catalyst for any of these stock price moves. The last time we heard anyone talking up the sector was more than a week ago, when Morgan Stanley gave a $38 price projection for Plug Power stock.

Three colorful arrows racing straight up on a black background

Image source: Getty Images.

Now what

What's an investor to do when stocks rise for apparently no reason? Check the numbers to see if they work, and if there's really a good reason to be buying these stocks. And when I look closely at Plug, FuelCell, and Flux Power, I really don't like what I see. None of these companies are profitable. For the last 10 years, Plug and FuelCell have done nothing but lose money and burn cash. According to data from S&P Global Market Intelligence, Flux Power has also been a perennial cash burner. 

About the only good thing that can be said for these companies at present is that they're doing a good job growing sales (although some better than others). Revenue at Plug Power is up 55% year over year through the first three reported quarters of 2020. Flux's sales in the first quarter of its new 2021 fiscal year more than doubled. FuelCell's sales gain, however, is an underwhelming 8.5%.

When you get right down to it, though, the business of business is not just to make sales, but to profit off those sales. So far, none of these three companies has quite figured out how to do that with consistency. If I were you, I wouldn't invest in them until they do.

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.