Plug Power (PLUG -7.02%) is a textbook example of how swiftly investor sentiment can flip. As of Aug. 31, the hydrogen stock had tumbled over 25% in the year. Then came September, and in a stunning turnaround, shares of Plug Power soared 48.4% during the month, according to data provided by S&P Global Market Intelligence.

The rally didn't stop there -- Plug Power stock has jumped another 77% already in October, logging 163% gains in just five weeks and hitting a 52-week high of $4.58 per share on Oct. 6.

Here's what's happening.

Green hydrogen fuel tanks.

Image source: Getty Images.

Why Plug Power stock keeps going higher and higher

Plug Power posted meaningful improvements in some numbers during its last earnings release in August. Its revenue grew by 21% year over year, and its gross margin improved from negative 92% in Q2 2024 to negative 31% in Q2 2025.

More importantly, Plug Power said it expects to exit 2025 with positive gross margin run rates, meaning its sales in Q4 should be able to cover production costs.

Plug Power's shift in focus from hydrogen fuel cell forklifts to electrolyzers in recent years appears to be paying off. Its electrolyzer revenue more than tripled to around $45 million year over year in Q2. The company is banking heavily on electrolyzers for growth while building green hydrogen plants to cut reliance on outside purchases and become a vertically integrated company.

Investors took note of this and continued to build a position in Plug Power through September. The stock surged even higher on Oct. 1 when Plug Power delivered its first 10 megawatt (MW) electrolyzer to Galp's Sines refinery in Portugal. It's a 100 MW deal and Plug Power's largest worldwide, with the remaining nine electrolyzers projected to be delivered by early 2026.

While this deal could open up more opportunities for Plug Power in Europe, one analyst believes the shift to alternatives sources of energy overall could hugely benefit Plug Power.

On Oct. 3, H.C. Wainwright analyst Amit Dayal upgraded Plug Power stock's price target to $7 per share from $3 a share. That implies 70% more upside potential even at current levels of around $4.10 apiece after Plug Power stock's stunning rally.

With electricity prices rising steadily across several states in the U.S., buoyed by demand, Dayal believes green hydrogen could find more takers if the trend continues.

So far, President Donald Trump has focused mainly on the nuclear energy industry, signing executive orders and inking a partnership with the U.K. government to accelerate nuclear capacity buildout amid rising demand for power from AI data centers. Dayal feels nuclear power could potentially be used to produce cheaper hydrogen through electrolysis and be paired with hydrogen electrolyzers to improve grid stability.

Dayal's massive price target upgrade has been the biggest recent catalyst for Plug Power stock, with shares jumping over 60% last week alone.

Read this before you buy Plug Power stock

Investors in Plug Power have waited for decades to see the company turn a profit. As the pioneer in the hydrogen industry, Plug Power has the technology, capabilities, and ecosystem to drive opportunities. It has, however, historically struggled to deliver on its plans and goals.

Things could finally be looking up, but the key still lies in execution. More importantly, Plug Power still has to work through its cash woes to increase production. I'll also take Dayal's views with a grain of salt, as his thesis about nuclear power boosting green hydrogen's prospects looks four to six years into the future.

Plug Power recently set an ambitious goal to exit 2028 with "overall profitability." If it can achieve that, the sky could be the limit for the stock. But that remains a big if for now, given Plug Power's history.