Three Mile Island restart in 2027: Microsoft's nuclear PPA and AI data centres

Summary. Constellation still expects the Crane Clean Energy Center, the former Three Mile Island Unit 1 in Pennsylvania, back online in 2027, returning 835 MW to the PJM grid. The restart rests on a 20-year power purchase agreement (PPA) with Microsoft signed on 20 September 2024, when the target was 2028. By 7 November 2026 the NRC had issued its final environmental assessment (18 September 2026) and allowed new fuel on site (1 July 2026), but the exemption and three licence amendments that restore power operations were still under review. The NRC expects a final decision in 2027. On 1 June 2026 FERC let Crane take over 760 MW of interconnection rights from two Eddystone units, so full grid deliverability need not wait for transmission work running to December 2030. The DOE closed a $1 billion loan in November 2025, and the licence ends on 19 April 2034. None of the six big-tech nuclear deals we compare discloses a price. For enterprise AI buyers, the lesson is how to read a cloud provider's carbon-free claims.

About this article. For CTOs, infrastructure leads and sustainability teams who buy cloud or colocation capacity for AI workloads. We checked the timeline and PPA against Constellation's releases and SEC filings, Microsoft's 2026 sustainability report, the NRC docket and press releases, Federal Register notices to 2 October 2026, the FERC order of 1 June 2026, PJM's 2025 project list and section 11 of Germany's Energy Efficiency Act as published online, all on 7 November 2026. Target dates are plans, not guarantees. This is not legal, investment or financial advice, and no vendor paid for inclusion. Researched with AI assistance and reviewed by our editorial team.

Where the Crane restart stands on 7 November 2026

Unit 1 shut down for economic reasons in 2019 but was never fully decommissioned, which is why a restart is possible. The milestones below come from Constellation, the NRC, PJM, the DOE and FERC.

The environmental finding is necessary but not sufficient. The NRC must still decide the exemption from the licence-termination rules in 10 CFR 50.82 and amendments covering technical specifications, security and the emergency plan, which would allow operation to 19 April 2034. It sent further questions on the emergency plan and technical specifications in September 2026 and lists no final decision.

The amendments were also contested. A local resident filed a hearing request on 27 April 2026; a licensing board ruled on 29 June and the Commission decided an appeal on 1 October 2026. We could not open the decision texts, so check docket 50-289-LA for anything still open. At a public meeting on 28 July 2026, FEMA and NRC staff said a full-participation emergency exercise will come before the emergency plan is finalised, as reported by WITF.

Inside 2027, the timing varies by source:

• Constellation's website: 2027, no month.

• Constellation's FERC waiver request: over 800 MW available in the second half of 2027.

• Constellation and NRC staff in July, as reported by WITF: approvals around May 2027, fuel load some time after June, no set grid date.

• NeutronRise, summarised by Neutron Bytes: NRC decision targeted for May 2027, fuel load and commercial operation late 2027.

The grid side: PJM and the FERC waiver

An NRC licence lets the reactor run; PJM decides how much of its output counts as capacity. PJM's May 2025 fast-track list includes Three Mile Island as a new nuclear resource requesting service in 2027, with 859 MW maximum output and 803 MW of capacity. Constellation's 835 MW is a different measure of the same plant.

PJM's first impact study tied Crane's full deliverability to transmission upgrades due as late as December 2030, according to Constellation's quarterly filing. Constellation asked FERC to move interconnection rights from Eddystone Units 3 and 4, two 380 MW dual-fuel units kept running under DOE emergency orders. FERC agreed on 1 June 2026 over the PJM market monitor's objections, finding the transfer could let Crane be fully operational before the end of 2030 without changing its queue position.

What Microsoft bought, and what it did not disclose

Constellation called the deal its largest-ever PPA. Microsoft buys the plant's energy to help match the power its PJM data centres use with carbon-free energy. Constellation's filing describes it as a purchase of the plant's output, with delivery subject to regulatory approvals. Microsoft's 2026 sustainability report presents Crane as its example of how conventional nuclear could fit a long-term carbon-free portfolio.

• Location matters. PJM serves 67 million people in all or parts of 13 states and the District of Columbia. Microsoft has not said which campuses or cloud regions the energy is matched against.

• The price is private. Neither company has published a price or structure beyond the 20-year term. Any quoted figure is an estimate.

• The contract outlasts the licence. A 20-year deal starting in 2027 runs into the late 2040s; the licence ends in April 2034. Constellation aims to run to at least 2054 and has told the NRC it plans to apply for renewal in the first quarter of 2029.

The DOE loan, closed under its Energy Dominance Financing programme, was the first under the current administration to get a conditional commitment and financial close at once. Restoration covers the turbine, generator, main power transformer and cooling and control systems, and Constellation planned to hire over 600 staff before restart.

How a nuclear PPA works

A PPA is a long-term contract to buy electricity, its environmental attributes, or both, from a specific generator. For data centres, three design choices matter more than the headline megawatts.

Physical, retail or virtual. Power can be delivered to the buyer's load, but more often the plant sells into the grid and the buyer gets energy and attributes through a retail supplier or a financial settlement. Meta's Clinton deal keeps the plant feeding the local grid while Meta buys its clean energy attributes.

Co-located or front-of-meter. A co-located data centre draws power behind the meter beside the plant; a front-of-meter deal uses the public grid. Talen's Susquehanna supply to Amazon moved to front-of-meter in April 2026, with Talen as retail supplier and PPL Electric Utilities handling delivery.

Annual or hourly matching. Most corporate claims net annual purchases against annual use; Microsoft reports matching 100% of its annual global electricity use with renewable energy in its 2025 financial year. A plant that runs around the clock can support hourly matching, which is harder and more meaningful. Google states a 24/7 carbon-free goal, and Constellation publishes an hourly-matching calculator. When a provider calls a region carbon-free, ask which method it means.

Contract terms that decide what a nuclear PPA is worth

• Volume shape. A fixed block leaves the seller to cover outages; an as-generated share leaves the buyer short when the unit is offline.

• Refuelling and outages. Plants can run up to two years between refuellings, says Constellation, but outages still happen. Check who buys replacement power and whether it carries attributes.

• Settlement point. If the plant settles at one grid node and your load sits at another, the price difference (basis) can erase savings.

• Attribute ownership. Confirm who owns the certificates, in which registry, and that they are not counted twice.

• Commercial operation date. Say what happens if the plant is late: delay damages, an exit right or interim supply.

• Deliverability. A licensed plant can still wait on transmission before it counts fully as capacity.

• Licence conditions. Where the term runs past a licence expiry, as Crane's does past 2034, check how a failed renewal is treated.

The big-tech nuclear deals compared

Figures come from each company's announcement or filing.

On 30 September 2026 Amazon agreed to take 690 MW from Calvert Cliffs, Maryland's only nuclear plant, with a retail supply agreement across PJM. On 6 October 2026 Google agreed to fund 890 MW of uprates plus a 2,700 MW supply deal, with terms to curtail non-critical load during grid stress, presented as a response to PJM's Bring Your Own Power proposal. On 27 October 2026 Constellation announced a conditional DOE loan commitment of up to $5 billion for uprates, still subject to due diligence and final documents.

Four kinds of nuclear deal, and what each adds

A restart or uprate adds generation that would not otherwise exist. Relicensing keeps clean output from disappearing but adds little, though Constellation's chief executive argues it matters as much as new sources. New reactors add the most but deliver last.

What this means for enterprise AI buyers

Almost no enterprise will sign an 835 MW contract. Your exposure comes through three channels.

Your cloud provider. Its procurement shapes the carbon profile you can report. Ask which grid your workloads run in, whether the region's carbon-free figure is annual or hourly, and whether it counts contracts not yet delivering, such as a 2027 restart. Our note on Azure East US 3 in Atlanta covers region selection on other dimensions.

Your colocation provider or retail supplier. In PJM, the Talen and Calvert Cliffs deals pair the PPA with retail supply. Smaller buyers can sometimes buy nuclear-backed retail supply; ask for the generator, the term and the attribute evidence.

Your own reporting. Keep location-based and market-based emissions separate, and do not count a provider's future contract as current supply. Treat 2027 as a target, not a capacity plan.

Worked example: what 835 MW means in practice

Illustrative calculations, not forecasts.

• Annual output. In its last year of operation the plant ran at maximum capacity 96.3% of the time, according to Constellation. At that rate, 835 MW × 8,760 hours × 0.963 = about 7.04 million MWh (7.04 TWh) a year.

• Average power. 835 × 0.963 = about 804 MW.

• AI load matched. At an assumed PUE of 1.3, 804 ÷ 1.3 = about 619 MW of average IT load on an annual basis.

• An enterprise cluster. A 500 kW AI deployment at an assumed PUE of 1.4 uses 0.5 × 8,760 × 1.4 = 6,132 MWh a year, about 0.09% of that output.

• Price sensitivity. Prices were not disclosed. Hypothetically, each $10/MWh of premium on 6,132 MWh adds $61,320 a year.

Hyperscalers buy whole plants; enterprises buy a share of a provider's portfolio, a retail product, or nothing nuclear.

Risks to watch

• Regulatory. NRC decisions on the exemption and amendments, FEMA's review of offsite plans and the full-participation exercise.

• Legal. Neutron Bytes reports that a federal lawsuit against the Palisades restart exemption, the route Crane follows, was dismissed in mid-2026 on jurisdictional grounds, leaving the merits untested.

• Operational. Operator licences are plant-specific; about 90 operators were in an 18 to 24 month licensing pipeline in July 2026, as reported by WITF.

• Grid. Check how PJM's interim studies treat Crane before relying on it as capacity.

• Cost allocation. PJM's Bring Your Own Power proposal and the White House Ratepayer Protection Pledge show how sensitive the question of who pays for data centre load has become.

• Beyond 2034. A 20-year contract depends on licence renewal.

India and EU notes

For Indian teams on US clouds. If inference runs in a US region, the provider's PJM or MISO contracts may shape the carbon figure it reports to you; ask for region-level data and the matching method. For hosting at home, see our guide to India data centre capacity for AI workloads and our explainer on India's cloud tax holiday to 2047.

For EU hosting. Germany's Energy Efficiency Act requires data centres to cover consumption on a balance-sheet basis with renewable electricity, 100% from 1 January 2027 under current law. Nuclear is not renewable, so a nuclear PPA does not help. The duty and the bill that would delay it are covered in our article on Germany's data centre renewable energy rule; efficiency limits are in our guide to Germany's EnEfG PUE cap from 1 July 2027.

A checklist for CTOs

1. Map each AI workload to a cloud region and grid operator.

1. Ask providers for the region's carbon-free share, the method (annual or hourly) and the reporting year.

1. Separate delivered supply from contracted future supply in any claim you repeat.

1. Ask your colocation provider whether it holds nuclear-backed supply, and get the evidence.

1. Keep location-based and market-based figures in your own reporting.

1. Plan capacity on what is energised, not on a restart date.

1. Revisit after the NRC decisions, the emergency exercise and grid synchronisation at Crane.

How eCorpIT can help

eCorpIT is a Gurugram-based technology organisation, founded in 2021, assessed at CMMI Level 5 and MSME certified, with senior-led engineering teams working across AWS, Microsoft and Google platforms. Our data centre and cloud networking team maps AI workloads to cloud regions and grids and builds energy and carbon dashboards from provider and colocation data. Talk to us at /contact-us/.

Last updated: 7 November 2026.

References

1. Crane Clean Energy Center — Constellation

1. Constellation to Launch Crane Clean Energy Center, Restoring Jobs and Carbon-Free Power to The Grid, 20 September 2024 — Constellation

1. Christopher M. Crane Clean Energy Center facility page (last reviewed 8 October 2026) — U.S. Nuclear Regulatory Commission

1. NRC Finds No Significant Environmental Impact from Proposed Crane Clean Energy Center Restart, No. 26-061, 9 June 2026 — U.S. Nuclear Regulatory Commission

1. Order Granting Waiver Request, Constellation Energy Generation, LLC, Docket ER26-2028-000, 195 FERC 61,162, 1 June 2026 — Federal Energy Regulatory Commission (copy hosted by RTO Insider)

1. Energy Department Closes Loan to Restart Nuclear Power Plant in Pennsylvania, 18 November 2025 — U.S. Department of Energy

1. Constellation Ahead of Schedule for Launch of Crane Clean Energy Center, 19 February 2025 — Constellation

1. Constellation Reports Second Quarter 2026 Results, Form 8-K Exhibit 99.1, 6 August 2026 — Constellation Energy Corporation (SEC EDGAR)

1. Constellation Energy Generation, LLC; Christopher M. Crane Clean Energy Center; Environmental Assessment and Finding of No Significant Impact, 25 September 2026 — Federal Register (GovInfo)

1. NRC Announces Opportunity to Request Hearing for Crane Clean Energy Center Restart License Amendments, No. 26-021, 24 February 2026 — U.S. Nuclear Regulatory Commission

1. Constellation Energy Generation, LLC; Establishment of Atomic Safety and Licensing Board, 15 May 2026 — Federal Register (GovInfo)

1. Atomic Safety and Licensing Board orders, 2026 (LBP-26-06, 29 June 2026) — U.S. Nuclear Regulatory Commission

1. Commission adjudicatory issuances, 2026 (CLI-26-13, 1 October 2026) — U.S. Nuclear Regulatory Commission

1. Three Mile Island reactor restart progresses through environmental review, public comments, 28 July 2026 — WITF

1. Inside Three-Mile Island's Quest to Clear Restart Hurdles (guest post by NeutronRise), 11 August 2026 — Neutron Bytes

1. PJM Chooses 51 Generation Resource Projects To Address Near-Term Electricity Demand Growth, 2 May 2025 — PJM Interconnection

1. Reliability Resource Initiative addendum (project list), Planning Committee, 6 May 2025 — PJM Interconnection

1. Form 10-Q for the quarter ended 30 June 2026, Note 3 Regulatory Matters — Constellation Energy Corporation (SEC EDGAR)

1. 2026 Environmental Sustainability Report — Microsoft

1. Constellation, Meta Sign 20-Year Deal for Clean, Reliable Nuclear Energy in Illinois, 3 June 2025 — Constellation

1. Talen Energy Expands Nuclear Energy Relationship with Amazon, Form 8-K Exhibit 99.1, 11 June 2025 — Talen Energy (SEC EDGAR)

1. Form 10-Q for the quarter ended 30 June 2026 — Talen Energy Corporation (SEC EDGAR)

1. Google signs advanced nuclear clean energy agreement with Kairos Power, 14 October 2024 — Google

1. Hourly Matching GHG Calculator — Constellation

1. Constellation and Amazon Announce 20-Year Power Purchase Agreement Adding 190 Megawatts of Nuclear Capacity at Calvert Cliffs, 30 September 2026 — Constellation

1. Google and Constellation Announce Landmark Agreement to Bring 890 MW of New Nuclear Capacity to PJM Grid, 6 October 2026 — Constellation

1. Constellation Secures Conditional DOE Loan Commitment of up to $5 Billion to Expand Nuclear Output, 27 October 2026 — Constellation

1. Energieeffizienzgesetz (EnEfG), section 11 — Federal Ministry of Justice (gesetze-im-internet.de)