Vistra Energy Corp. (VST) stock plummeted 5.1% in the post-market trading session on Thursday, following a mixed trading day where the stock initially surged 7% on strong Q4 earnings but later gave up most of the gains.

The reversal in stock price movement seemed to be driven by skepticism from analysts about the company's ambitious nuclear energy expansion plans and its reliance on AI data centers' demand. While Vistra reaffirmed its 2025 guidance and reported a record 2024 performance, analysts raised concerns about the challenges facing nuclear energy companies, such as the long construction periods, high costs, and the volatility in demand from tech giants like Microsoft.

According to some analysts, the recent pullback in Microsoft's data center leases, amounting to a couple of hundred megawatts, cast doubts on the nuclear-AI connection that has fueled the rally in nuclear stocks over the past year. The fate of nuclear energy companies like Vistra could fluctuate based on the whims and intentions of tech companies, making their valuation volatile and speculative.