What happened

It's starting to look like it will be another good week for alternative energy stocks.

Shares of hydrogen fuel cell stock Plug Power (NASDAQ:PLUG) are up a respectable 6.1% as of 1:20 p.m. EST, while Plug rival Bloom Energy (NYSE:BE) and Clean Energy Fuels (NASDAQ:CLNE) (a natural gas stock) are doing twice as well -- surging 14.2% and 12.9%, respectively.

Curiously, although it's sporting the smallest stock price gains of the three, Plug Power stock is the only one of these stocks with good news supporting it.

Three colorful arrows racing straight up on a black background

Image source: Getty Images.

So what

Over the weekend, Barron's magazine called out Plug Power as "one of this year's stock market standouts," with the stock up sixfold in 2020, and setting the stage for a $1 billion stock offering that promises to give Plug enough ready cash to fuel its growth for years to come.  

Barron's sad Plug is partly benefiting from the widespread popularity of renewable energy, "electric vehicles, hydrogen power, and the fuel cells" stocks among investors this year. (And this wide-ranging call-out of renewable energy technologies may explain investors' enthusiasm for Bloom Energy and Clean Energy fuels today.)

But in the magazine's view, Plug's popularity with investors is also a function of its having signed up "two big names" -- Walmart and Amazon -- as customers for its fuel cell-powered forklifts. Barron's notes that this has been good news for Walmart and Amazon because, thanks to their having negotiated warrants to purchase Plug stock as part of their sales agreements, they've been able to profit from the rising price of Plug Power shares -- meaning they essentially "got paid to buy its products."

Now what

Here's the real question for investors as they think through whether Plug's sales success will continue:

Plug recorded a lot of sales to Walmart and Amazon largely because it was selling warrants for its stock alongside fuel cells. (Every $50 million worth of fuel cells purchased entitled Walmart and Amazon to buy another batch of warrants, according to Barron's). But is Plug going to have to continue pairing warrants with fuel cells for every customer it tries to sell fuel cells to, to incentivize sales of its fuel cells?

And what happens to Plug's sales growth if it tries to sell the fuel cells without the stock warrants? It might not have any problem at all as fuel cells grow in popularity around the globe. But it might have a lot of problems if all that companies -- and investors -- are really interested in owning is red-hot Plug stock.

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.