Hydrogen technology production company Plug Power reported better-than-expected first quarter sales, which might keep short sellers on the run in Tuesday trading.

Monday, Plug reported first-quarter operating loss of about $109 million from sales of $163.5 million. Wall Street was looking for a $110 million loss from sales of about $140 million, according to Bloomberg. A year ago, Plug reported an operating loss of about $180 million from sales of about $134 million.

Shares were up 6.91% in after-hours trading to $3.76. Plug Power stock rose 12.8% in regular trading, while the S&P 500 and Dow Jones Industrial Average both gained about 0.2.%.

There wasn't much news ahead of the earnings report that would explain the Monday jump.

The best explanation might have been investor positioning. Plug Power is a popular short, with some 350 million shares borrowed and sold by bearish investors who expect the stock to decline.

That's about 25% of the stock available for trading. That is high short interest. The average short interest for stocks in the Russell 2000 small capitalization index is about 8%.

Short sellers might not have wanted to take the chance that Plug said something that sends shares higher -- like higher-than-expected sales.

In its fourth-quarter report on March 2, Plug reported a smaller-than-expected loss, and the stock jumped 23%. Management also expressed its expectation to produce positive earnings before interest, taxes, depreciation, and amortization, or Ebitda, by the fourth quarter.

It was the largest positive jump for Plug following earnings over the past 10 years. The worst drop was 40% after the company reported weaker-than-expected third-quarter 2023 earnings.

Plug isn't profitable yet. For 2026, Wall Street projects a roughly $350 million operating loss from about $800 million in sales.

A lack of profits hasn't stopped investor enthusiasm. Through Monday trading, shares were up more than 300% over the past 12 months. Still, developing green hydrogen technology has been difficult. Shares remain down from a five-year high of more than $46.

Green hydrogen generally refers to hydrogen gas produced from splitting water into hydrogen and oxygen using renewably sourced electricity. Plug said hydrogen fuel sales grew 22% year over year.

The company ended the quarter with about $800 million in cash. Wall Street projects cash use of about $250 million in 2026.