The mechanism. Nuclear plants sitting next to data centers looked like the cleanest arbitrage in the power sector: sell electricity straight to a hyperscaler behind the meter, skip the congested grid, and charge a premium no utility rate case would ever allow. Then FERC said no. In November 2024, on a 2-1 vote, the Commission rejected an amended interconnection service agreement that would have let Talen Energy expand Amazon's co-located data center load at the Susquehanna nuclear plant in Pennsylvania from 300 MW to 480 MW — finding that PJM Interconnection failed to prove the deal's non-standard terms were justified by any reliability need unique to that site. FERC reaffirmed the rejection on rehearing in March 2026, and Talen is now pursuing an appeal at the Fifth Circuit. Separately, FERC's December 18, 2025 order found PJM's tariff itself unjust and unreasonable for failing to clearly define co-location rules, and directed PJM toward new "front-of-the-meter" transmission-service options — arrangements where colocated load pays standard grid-service costs rather than sidestepping them entirely. Both moves point the same direction: regulators are narrowing the path to the isolated, premium-priced nuclear-to-hyperscaler deal.

Who is exposed. Constellation Energy (CEG), the largest U.S. nuclear fleet owner, was counting on behind-the-meter contracts to re-rate the value of plants like Calvert Cliffs and its Susquehanna-adjacent peers well above wholesale power prices; the stock fell roughly 12.6% on the initial rejection news as investors repriced that upside. The company has since pushed FERC for clearer rules rather than a blanket block, but clarity is cutting toward front-of-the-meter economics, not the isolated-load premium it wanted. Talen's Susquehanna arrangement is the direct casualty — the specific deal FERC voided twice — leaving Talen to litigate rather than monetize. Vistra, though outside this ticker universe, saw a comparable hit, underscoring this is a sector-wide repricing of the co-location thesis, not a one-company problem.