What happened

Shares of hydrogen fuel cell company Plug Power (PLUG -4.93%) tumbled 4.6% through 10:45 a.m. EST this morning in response to a confluence of factors -- both macro- and microeconomic.

The big news frightening investors today is of course the jobs report. Nonfarm payrolls grew a stronger-than-expected 311,000 in February, reported the Labor Department this morning, heightening fears that the Federal Reserve will raise target interest rates faster, higher, and for longer than hoped, diminishing the value of hypothetical future profits for still-unprofitable growth stocks like Plug Power.  

That's one reason for Plug investors to worry, but it's not the only reason.

So what

You see, two additional, fuel cell-specific factors are weighing on Plug stock today. First and foremost was rival FuelCell Energy's (FCEL -7.60%) earnings report yesterday morning, which showed the company growing revenues strongly and losing less money than expected but still losing quite a lot of money. Although investors responded positively to FuelCell's report initially yesterday, the enthusiasm quickly waned, and FuelCell ended the day up less than 2% and has lost even that small gain already today.

Next came a new analyst rating on a third fuel cell stock, Ballard Power Systems (BLDP -4.80%). Scotiabank initiated coverage of Ballard this morning but gave the stock only a muted "sector perform" rating (i.e., "hold") and worried aloud about "the company's near-nil gross profits and negative earnings."  

Now what

"Near-nil" gross margins and "negative earnings?" Does that remind you of anyone else in the fuel cell sector? Does it perhaps even remind you of almost everybody else in the fuel cell sector?

Because as it turns out, of the four best known fuel cell plays, Bloom Energy (BE -5.10%) is actually the only one with gross profit margins anywhere above "nil," while everybody else has a negative gross. And of course, once you subtract operating costs, all four of these companies -- Bloom included -- are reporting deeply negative earnings and have been doing so for years.

Fact is, out of these four, Bloom and Plug actually look in the best shape, with analysts hopeful they might start earning generally accepted accounting principles (GAAP) profits no earlier than 2025. Analyst forecasts don't show profits emerging for Ballard, however, until 2027 -- or for FuelCell...ever.

Long story short, there's plenty news afoot to make Plug investors nervous today and plenty to worry investors in any fuel cell stock, period.