Microsoft has signed a 20-year power purchase agreement with Constellation Energy to restart Three Mile Island Unit 1 in Pennsylvania, securing 835 megawatts of carbon-free electricity for its data centers at a cost of approximately $1.6 billion. The facility, rebranded as the Crane Clean Energy Center, is expected to begin commercial operations by 2028, though regulators have granted a waiver that could accelerate the timeline to 2027.

Why Is Microsoft Turning to Nuclear Power for AI Data Centers?

The energy demands of artificial intelligence have become staggering. Training and running large language models (LLMs), which are AI systems that process and generate human language, requires enormous amounts of electricity. Microsoft's decision to restart a nuclear reactor underscores just how desperate tech companies have become for reliable, carbon-free power sources. Unlike solar or wind farms, nuclear plants operate continuously, providing the steady baseline power that data centers need to run 24/7.

The Three Mile Island restart is particularly symbolic. Unit 1, the reactor being restarted, operated safely for decades before being shut down in September 2019 for economic reasons, not safety concerns. It was Unit 2 that experienced the partial meltdown in 1979, making this a chance to rehabilitate the site's reputation while addressing a critical infrastructure gap.

What Are the Economic and Employment Implications?

Beyond powering data centers, the project carries significant economic weight. The restart is expected to create approximately 3,400 jobs and generate more than $3 billion in state and federal tax revenues over the life of the 20-year agreement. For Pennsylvania, a state with a history of industrial decline, this represents a substantial economic injection.

Constellation Energy, the company investing $1.6 billion to restart the plant, has secured a 20-year revenue stream from one of the world's most creditworthy counterparties. This arrangement provides the utility with financial stability while giving Microsoft guaranteed access to clean power for its AI infrastructure.

How Is This Deal Reshaping Regional Energy Markets?

The Three Mile Island restart has immediate ripple effects across the PJM Interconnection, the regional grid operator serving 13 states and Washington DC. When a single corporate buyer locks up 835 megawatts of capacity for two decades, that electricity is unavailable to other users, including cryptocurrency miners operating in the same region.

• Capacity Constraints: Bitcoin miners and other energy-intensive operations competing for power in the PJM region face tighter supply and potentially higher prices as AI companies vacuum up available capacity.
• Long-Term Contracts vs. Spot Markets: Crypto miners who have already secured long-term energy contracts or own their generation assets are in a stronger negotiating position than those still buying power on volatile spot markets.
• Regulatory Acceleration: The June 2026 waiver allowing faster grid connection at Three Mile Island signals that federal and state regulators are willing to fast-track nuclear projects that address energy deficits, potentially opening doors for similar deals.

What Does This Signal About the Future of AI Infrastructure?

Microsoft's nuclear bet reflects a broader shift in how tech companies approach energy security. Rather than relying on traditional grid infrastructure, hyperscalers (massive cloud computing companies) are increasingly pursuing long-term power purchase agreements with utilities and investing in dedicated generation assets. This trend suggests that AI's energy demands are no longer a temporary spike but a permanent structural change in how America consumes electricity.

The regulatory environment is also evolving in favor of nuclear. The waiver granted in June 2026 demonstrates that both federal and state authorities recognize the urgency of the energy crisis and are willing to streamline approval processes for projects that can deliver reliable, carbon-free power at scale.

Steps for Understanding AI's Energy Impact on Your Region

• Check Your Grid Operator: Identify which regional transmission organization (RTO) or independent system operator (ISO) manages electricity in your area. The PJM Interconnection covers much of the Northeast and Midwest, but other regions like ERCOT in Texas or CAISO in California operate under different rules.
• Monitor Power Purchase Agreements: Track announcements from major tech companies and utilities about long-term energy deals in your region. These agreements can affect local electricity prices and availability for other consumers and businesses.
• Understand the Carbon Trade-off: While nuclear power is carbon-free, restarting aging reactors involves environmental remediation and waste management considerations. Research your region's energy mix and how AI infrastructure investments align with local climate goals.

The Three Mile Island restart represents a pivotal moment in how technology infrastructure and energy policy intersect. Microsoft's $1.6 billion commitment signals that AI companies are willing to make massive, long-term bets on nuclear power to secure the electricity their systems demand. For investors, policymakers, and energy consumers, this deal offers a glimpse into how the next decade of infrastructure development will unfold.