New York, Jan 8, 2026, 15:04 EST — Regular session
Constellation Energy shares were down about 4.2% at $324.54 in mid-afternoon trading on Thursday, extending a two-day slide as investors digested the close of its Calpine acquisition. The stock fell 4.5% on Wednesday to $338.63, its third straight session of losses.
Constellation said on Wednesday it completed the purchase of Calpine from Energy Capital Partners, a deal that pushes the nuclear-heavy generator deeper into natural gas and geothermal power. CEO Joe Dominguez said U.S. demand for power “is surging,” pointing to data centers and other big loads, while Calpine CEO Andrew Novotny said the combined group “has the assets that power America today.” Constellation
Constellation and Calpine together now have 55 gigawatts of generation capacity — a measure of maximum output — and a larger footprint in Texas and California, the company said. The Wall Street Journal said Constellation valued the cash-and-stock deal at $26.6 billion including assumed debt when it was announced last year.
The broader market tone was cautious. U.S. stocks edged lower on Thursday with big tech weighing, while investors waited for Friday’s U.S. employment report, Reuters reported. Shares of power producer peers Vistra and NRG Energy were down about 2.6% and 3.8%, respectively.
Separately, the Nuclear Regulatory Commission approved a major digital upgrade for safety-related instrumentation and controls — the sensors and control gear tied to reactor protection — at Constellation’s Limerick nuclear plant in Pennsylvania, the American Nuclear Society reported. It pegged the project at $167 million and cited federal officials calling it the first large-scale approval to replace multiple analog safety systems with a single digital protection system at an operating U.S. nuclear plant.
For investors, the near-term focus is execution: what the Calpine assets contribute to cash flow, and how quickly the company can show early integration progress. The enlarged fleet also leaves results more exposed to swings in regional power prices and gas-generation margins.
But the downside case is not subtle. Integration can run over budget, divestitures tied to regulatory reviews can shift timetables, and any delay in promised synergies — cost savings from combining operations — could keep pressure on the stock.
Constellation has not announced the date for its next quarterly results, but Nasdaq’s earnings calendar estimates the report around Feb. 17. Traders will look for updated guidance and the first clean read on Calpine’s early performance inside the group.
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