Constellation, the largest clean energy producer in the U.S., is spending $800 million to upgrade two Illinois nuclear plants specifically to meet surging electricity demand from AI data centers. The upgrades will add a combined 158 megawatts to the grid, enough to power roughly 100,000 homes every year. Work at the Byron plant began in March 2026 and is expected to be completed by 2028, while the Braidwood facility will begin upgrades in spring 2027 and finish by 2029.

This investment marks a dramatic reversal for an industry that was on the brink of collapse just a few years ago. Nuclear plants in Illinois were facing shutdown due to economic pressures, but state legislation and the explosive growth of AI infrastructure have transformed the outlook. Illinois now leads the nation in nuclear energy generation, producing more electricity from its 11 reactors across six plants than any other state, according to U.S. Energy Information Administration data. Today, just over half of the state's electricity comes from nuclear power, followed by fossil fuels at 31 percent and renewables at 15 percent.

Why Are Data Centers Driving a Nuclear Energy Revival?

The surge in AI data center construction has fundamentally changed the energy calculus for nuclear power. Unlike solar and wind farms, which generate electricity intermittently depending on weather conditions, nuclear plants operate continuously at full capacity 24 hours a day, seven days a week. This reliability is exactly what large-scale AI infrastructure requires to train and run massive language models and other compute-intensive systems.

"Solar, wind, hydro, all the other renewable sources, you can almost consider them part-time power. Nuclear plants are on 24/7. We don't rely on any weather, like the whole building could freeze, and the plant would keep going," said Adam Schuerman, Vice President at Constellation.

Adam Schuerman, Vice President at Constellation

Data centers seeking reliable power have become the anchor tenant for nuclear energy's comeback. Companies building AI infrastructure need guaranteed, uninterrupted electricity supply, and nuclear plants can provide that in a way renewables cannot. This demand has given nuclear operators like Constellation the economic justification to invest in expensive upgrades that would have been impossible to justify just five years ago.

How Are States Supporting Nuclear Energy Growth?

• Zero-Emission Credits: Illinois passed the Future Energy Jobs Act in 2016, which established zero-emission credits and provided subsidies to nuclear plants. This policy helped keep Constellation's Clinton Power Station from closing.
• Carbon Mitigation Credits: The Climate and Equitable Jobs Act of 2021 introduced carbon mitigation credits that supported plants like Braidwood and Byron, which were on the verge of shutting down that year.
• Lifting the Nuclear Ban: In January 2026, Governor J.B. Pritzker signed the Clean and Reliable Grid Act, ending a decades-old moratorium on building new large-scale nuclear plants in Illinois, signaling to investors that the state is open for nuclear development again.

These policy changes stabilized the nuclear industry, preserving jobs and maintaining a reliable source of carbon-free energy. Without state support, many of these plants would have closed permanently, eliminating a crucial source of baseload power that can operate regardless of weather conditions.

What Role Will Nuclear Play Alongside Renewables?

While nuclear is experiencing a renaissance, experts emphasize that it cannot be the only solution to Illinois' growing energy demands. Utilities and grid operators argue that a diversified energy portfolio is essential. Wind and solar projects can be built much faster than nuclear upgrades, typically within 18 months and connected to the grid in less than three years, compared to the three-year timeline for these nuclear uprates.

"The beautiful thing about wind and solar is they don't produce emissions, they also produce a lot of electricity when the sun is shining and the wind is blowing. But you do have those periods of time, where they are intermittent or they are not running and you're relying on additional resources out on the grid to help support reliability as well as just add stability to the marketplace for power," explained Matt Tomc, Vice President of Regulatory Policy and Energy Supply at Ameren.

Matt Tomc, Vice President of Regulatory Policy and Energy Supply at Ameren

Ameren, the utility company covering central and southern Illinois and parts of Missouri, views nuclear generation as a necessary "anchor" for the state's grid as Illinois works toward ambitious clean energy goals, including zero carbon emissions by 2050. However, both Ameren and ComEd, the primary electricity provider for Chicago and northern Illinois, have cautioned that increasing nuclear power alone will not be enough to solve the state's looming energy challenges.

The Braidwood and Byron upgrades represent a pragmatic approach to meeting immediate demand while the state continues developing renewable capacity. These plants will provide the stable, 24/7 power that AI data centers require, while wind and solar projects can be developed in parallel to diversify the energy mix and reduce reliance on any single source. For Illinois, which is considered the birthplace of nuclear power dating back to 1942, this investment signals a return to its historical strength in nuclear technology and a recognition that different energy sources serve different purposes in a modern grid.