Amazon signed a long-term power purchase agreement with Constellation Energy at Calvert Cliffs nuclear facility.

Constellation Energy and Amazon have announced a 20-year power purchase agreement to support continued investment in and expansion of the Calvert Cliffs Clean Energy Center in Maryland. The plant, located on the western shore of the Chesapeake Bay near Lusby in Calvert County, comprises two Combustion Engineering 850 MWe pressurised water reactors and generates approximately 40% of Maryland's total power and around 87% of the state's clean energy.

The agreement will enable more than $3 billion in Maryland infrastructure investment, including state-of-the-art improvements across the entire facility and approximately 190 MWe in total of new generating capacity coming online between 2030 and 2032.

The deal represents a significant strategic shift for Amazon after it scrapped earlier plans to build a data centre campus directly next to the plant following local opposition and political changes in Maryland. In a recent primary election, voters ousted all three county commission members who had opposed a data centre moratorium. Constellation remains open to hosting a data centre at Calvert Cliffs, though David Dardis, Constellation's Senior Executive Vice President and chief external affairs and growth officer, said "nothing is in the works" and emphasized the company would "only do so in partnership with Calvert County and other important stakeholders."

Under the new arrangement, Amazon will purchase 690 MWe of power overall. Critically, all electricity generated at Calvert Cliffs will continue flowing into the regional PJM Interconnection grid rather than being fed directly into isolated data centres—a "front-of-the-meter" grid strategy rather than a "behind-the-meter" direct hookup. This approach provides a blueprint for how tech companies can secure nuclear capacity without angering communities or drawing regulatory fire for hoarding grid resources.

The long-term revenue certainty enables Constellation to pursue a 20-year operational licence renewal for the facility, with current reactor licences running to 2034 and 2036, while exploring deployment of next-generation technologies such as small modular reactors. By committing to 690 MWe long-term, Amazon also stabilises its utility exposure across the highly contested 13-state PJM regional power market, insulating AWS from surging electricity prices driven by the sudden explosion of regional data centre development.

This is Amazon's first agreement to fund a nuclear uprate project, adding to its expanding nuclear footprint that includes a power deal with Talen Energy at Susquehanna NPP in Pennsylvania and over $500 million invested in SMR development in Washington state.

Calvert Cliffs currently yields approximately 1,790 MWe. Planned upgrades will boost the facility's baseline capacity to 1,980 MWe—an expansion equivalent to all utility-scale wind and solar generation currently operating in Maryland. To unlock the additional 190 MWe, Constellation will implement major mechanical and thermal modifications, including refining reactor equipment, optimising core fuel management, upgrading high-pressure turbines, and modifying instrumentation to handle higher steam flow and heat generation safely and efficiently. The multi-year overhaul will occur in phases, with new capacity projected online between 2030 and 2032. Since Amazon will not siphon this power directly, the newly generated electricity will go straight into the regional grid, providing enough baseline power to support up to 1.5 million local homes while fulfilling Amazon's contractual energy offsets.

"This agreement demonstrates how private investment can strengthen critical energy infrastructure," said Constellation Chairman, President & CEO Joe Dominguez. "Amazon's commitment supports the long-term operation of Calvert Cliffs for generations to come and creates a strong foundation for future investment in both the facility and in advanced nuclear technologies."

Kerry Person, Vice President of AWS Global Operations & Data Center Delivery, noted: "Amazon is committed to investing in carbon-free energy to strengthen the grid and benefit the communities where we operate. This long-term agreement with Constellation sustains the continued operation and expansion of Maryland's largest source of carbon-free energy, supports hundreds of jobs, and brings significant new generation to the regional grid."

Constellation's nuclear partnerships have proliferated. The company plans to reopen Three Mile Island in Pennsylvania, renamed the Crane Clean Energy Center, next year under a 2024 20-year agreement with Microsoft. In June 2025, Constellation signed a 20-year PPA with Meta for the Clinton Clean Energy Center in Illinois, expected to support relicensing and add an additional 30 MWe. Earlier this year, Constellation also signed a multi-contract deal with Walmart to supply 176 MW over two staggered 15-year terms starting in 2029 and 2030, with baseline electricity drawn from the Dresden Clean Energy Center in Illinois to power new distribution infrastructure.