Constellation Energy and Amazon announced on Sept. 30 an energy deal supporting more than $3 billion in infrastructure investment at Maryland’s 1.79 GW Calvert Cliffs nuclear plant, including a planned 190 MW upgrade.
The 20-year deal covers 690 MW, including additional capacity, and provides Constellation with revenue certainty to seek two more decades to operate the plant located on the western shore of the Chesapeake Bay in Calvert County.
Few details have been revealed about what will actually be designed and built. Constellation says the investment will include “state-of-the-art improvements” across the plant, but has not publicly identified major changes to equipment, engineering or construction contractors or how the announced funding of more than $3 billion will be split between upgrading, modernizing the plant and work to support longer operation.
Plans to ramp up production predate Amazon. In February 2025, Constellation announced approximately $100 million in critical upgrades to the plant’s electrical system and equipment that it said would allow for a potential license renewal and future power increases.
The scheduled works included the renewal or replacement of pumps, motors, valves and control rod systems, as well as the overhaul of a 13 kV transformer.
Preliminary analysis at the time showed that new upgrades could increase Calvert Cliffs’ electricity output by about 10 percent. Constellation also said it was investing $68 million in 24 electrical breakers to upgrade the plant’s substation and help enable future customer service on the grid. In November 2025, the utility put a number on the proposed increase — 190 MW — and said “new equipment and technology” would be required. Amazon’s long-term commitment now makes the upgrade possible, according to Constellation.
Uprate Faces Review, license renewal imminent
The US Nuclear Regulatory Commission held a closed meeting with Constellation on October 1 to discuss the upcoming license modification applications for Calvert Cliffs Units 1 and 2. The agency did not say whether those requests involve the newly announced update.
Turbine-generator equipment at Constellation’s Calvert Cliffs nuclear plant in Maryland. The planned 190 MW increase follows previous plant investments linked to increased production, including electrical system and equipment upgrades announced in 2025.
Photo courtesy of Constellation Energy
The Commission’s senior public affairs officer, Scott Burnell, told ENR in an Oct. 1 email that the agency has no additional information about the meeting. Plant owners publicly submit requests to update or renew licenses, he says, and the commission can only provide a review schedule after finding an acceptable application.
Constellation no immediately respond to ENR’s request for comment.
The Oct. 1 meeting follows an earlier closed session between the agency and Constellation on Feb. 25, specifically about potential power-up amendment requests. The commission did not identify the plants involved in this meeting.
Burnell notes that Calvert Cliffs was the first U.S. nuclear plant to be approved for a power increase, in 1977. The commission approved 5.5 percent step increases for each of its two Combustion Engineering pressurized water reactors, increasing authorized thermal output by 140 MWt per unit.
In 2009, the agency approved a second, smaller increase of 1.4%, or 37 MWt, for each unit, classified as a measurement-uncertainty-recapture increase. Constellation’s application proposed installing high-precision Caldon feedwater flow instrumentation that reduced measurement uncertainty enough to increase the authorized thermal output of each reactor from 2,700 MWt to 2,737 MWt.
ENR file
Calvert Cliffs Nuclear Expansion
Over a decade of ENR reporting
ENR followed efforts to expand Calvert Cliffs from the push for a third reactor through funding and regulatory pushbacks.
February 24, 2010
UniStar sought a new Calvert Cliffs reactor as Bechtel and Areva held the EPC contract and the project competed for federal loan support.
October 14, 2010
Constellation withdrew after objecting to an $880 million federal loan guarantee rate for the roughly $10 billion reactor project.
September 5, 2012
NRC ruled that UniStar could not build and operate the proposed $9.6 billion, 1,600 MW unit under its foreign ownership structure.
ENR previously tracked the Calvert Cliffs Unit 3 expansion proposal, including Bechtel-Areva’s engineering, procurement and construction team; Constellation’s 2010 withdrawal from the roughly $10 billion project amid a dispute over federal loan guarantee costs; and the federal nuclear regulator’s subsequent foreign ownership ruling. Bechtel also served as the builder and consulting engineer for the existing plant, according to Constellation. Instead, the current proposal would add generation from the site’s two operating reactors.
Workers guide a large power transformer into position during installation. Constellation installed a $4.8 million, 151-ton transformer during an outage of Calvert Cliffs Unit 1 in 2026 that included nearly $90 million in equipment upgrades. The work in the photo is not at Calvert Cliffs.
Photo/Adobe
Calvert Cliffs was also the first nuclear plant in the United States to receive a renewed operating license, in 2000—Burnell says. Units 1 and 2 are currently licensed until 31 July 2034 and 13 August 2036 respectively.
The commission granted one-time waivers to Constellation in November 2024 that allowed subsequent license renewal applications to receive “timely renewal” protection if they were filed at least three years before existing licenses expired and accepted for registration. To qualify, Constellation would have to apply by July 31, 2031 for Unit 1 and by August 13, 2033 for Unit 2. If the applications are accepted for the record, existing licenses would remain in effect until the agency makes final decisions on the renewal applications.
Earlier this year, a 27-day Unit 1 refueling outage involved nearly $90 million in equipment upgrades and more than 1,500 skilled workers. The work included the installation of a $4.8 million, 151-ton transformer and $14.9 million in electrical equipment upgrades.
Constellation has not disclosed when it intends to submit its next license renewal or upgrade applications. Nor has it revealed when work would specifically begin on the 190 MW increase, nor have the main teams and contractors involved been identified.
