PJM Interconnection, the regional U.S. grid operator, has told Constellation Energy that some of the transmission work required to link the former Three Mile Island nuclear plant in Pennsylvania to the grid will likely not be completed until 2031. That timeline is about four years later than Constellation had planned, company representatives said at the CERAWeek energy conference in Houston.
Constellation is advancing a program to restart the shuttered nuclear unit, which it is renaming the Crane Clean Energy Center, with the intention of supplying electricity to Microsoft data centers. Company officials maintain that the plant itself will be ready to generate electricity on the earlier timetable, and they are engaging with PJM and transmission owners to try to accelerate the grid interconnection work.
David Dardis, Constellation's chief external affairs and growth officer, said at the conference: "We will have it ready to go in 2027." He also confirmed the company is in discussions with PJM and transmission owners to seek ways to reduce the interconnection timeline.
In its initial review of Constellation's interconnection proposal, PJM concluded that completion of necessary transmission upgrades is unlikely before 2031. Constellation said it is actively talking with the relevant transmission owners to explore options for speeding up those upgrades.
Investors reacted to the update: shares of Constellation dipped roughly 3% after the report of the extended interconnection schedule.
The company announced in 2024 that it had contracted with Microsoft to reopen the site, which has not operated as a producing nuclear plant since it was fully shut. No U.S. nuclear facility that was fully shuttered has previously been restarted. The company and industry observers note that there are three U.S. plants currently in the process of seeking to restart as demand from large data centers and broader electrification trends increases.
Context and next steps
- Constellation will continue to ready the plant to begin generating by the 2027 target date the company has set.
- PJM's current assessment identifies transmission upgrades that extend the interconnection window to 2031 absent acceleration by transmission owners or changes to the interconnection plan.
- Conversations between Constellation, PJM and transmission owners are ongoing to evaluate whether the timeline can be shortened.