Amazon Web Services has locked in carbon-free power for one of its most important East Coast data center regions, signing a 20-year power purchase agreement with Constellation Energy for 690 megawatts from the Calvert Cliffs Clean Energy Center in Maryland. The deal, reported October 1 by Data Center Dynamics, includes roughly 190 megawatts of new generating capacity coming online between 2030 and 2032.

What the Agreement Covers

The agreement is between AWS and Constellation, which operates Calvert Cliffs in Lusby, Calvert County. The plant is Maryland’s only nuclear station and has a current capacity of 1.78 gigawatts. Amazon’s 690 megawatts is therefore a substantial slice of the plant’s output.

Constellation will invest more than $3 billion in infrastructure improvements to support the expanded capacity. Constellation also announced a related retail supply agreement covering the 13-state PJM market, which broadens the commercial arrangement beyond the plant itself.

Executives Frame It as Long-Term Supply

Joe Dominguez, Constellation’s CEO, said “Amazon’s commitment supports the long-term operation of Calvert Cliffs for generations to come.” Kerry Person, a vice president at AWS, said “this long-term agreement with Constellation sustains the continued operation and expansion of Maryland’s largest source of carbon-free energy.”

The wording matters. Both sides describe the deal as sustaining an existing plant and expanding it, not simply drawing from the grid. That is the structure data center operators now prefer: contracts long enough to justify capital investment by the generator, tied to specific assets they can point to when reporting emissions.

A Reversal on the Adjacent Campus

The agreement arrives after a change in Amazon’s plans for the same site. The company had planned an eight-building data center campus of about 2.46 million square feet and 500 megawatts adjacent to the plant, and withdrew that proposal in August 2026. The power agreement does not bring the campus back, but it shows Amazon still values the plant’s output.

Amazon is pursuing other Maryland projects. AWS is developing a separate campus at Quantum Frederick Park in Adamstown, and it recently bought a Baltimore-area office and data center site through a sale-leaseback arrangement with T. Rowe.

Why Nuclear Keeps Winning Contracts

For hyperscalers, firm, carbon-free power is scarcer than land or chips. Wind and solar cannot supply the around-the-clock load that AI clusters demand, and grid interconnection queues are long. An existing nuclear plant with expansion potential offers both supply and a credible emissions story.

The 20-year term also gives Constellation the revenue certainty to finance the more than $3 billion in upgrades. That is how new capacity gets built without waiting on regulators or speculative merchant markets.

What It Means for Rivals

Amazon is moving to secure its power supply ahead of competitors in the Mid-Atlantic, one of the densest data center regions in the country. Microsoft and Google have also pursued nuclear arrangements, and each deal removes carbon-free capacity from the pool available to the others.

For utilities and independent generators, the deal is a template: long-term contracts with hyperscalers, tied to existing plants, with upgrades paid for through the offtake. For data center developers without their own power arrangements, the lesson is harder. As hyperscalers lock up nuclear output for decades, the remaining supply will cost more, and sites without secured power will fall behind.