A data centre needs power every hour, and nuclear plants produce power steadily, day and night, without direct carbon emissions. That makes nuclear attractive to companies building AI data centres. Today nuclear supplies a meaningful share of data centre electricity, and several technology companies have signed agreements to restart old reactors or buy power from new small ones. The catch is time: restarts take years, and most new small reactors are not expected before 2030.
Where nuclear stands today
The International Energy Agency estimates that nuclear supplies 15% of the electricity used by data centres worldwide. It expects that after 2030 small modular reactors enter the mix, providing a source of baseload low-emissions electricity to data centre operators, and reports that technology companies have plans to finance more than 20 GW of them.
What a small modular reactor is
The International Atomic Energy Agency describes small modular reactors as advanced reactors that produce electricity of up to 300 MW(e) per module, designed to be built in factories and shipped for installation as demand arises, as a single module or several together. It reports four in advanced stages of construction, in Argentina, China and Russia.
The agreements announced so far
| Agreement | What it is | Timing stated by the company |
|---|---|---|
| Constellation and Microsoft | A 20-year power purchase agreement to restart Three Mile Island Unit 1 as the Crane Clean Energy Center, about 835 MW | Expected online in 2028, subject to regulatory approval (announced September 2024) |
| Google and Kairos Power | Up to 500 MW of new power from multiple small modular reactors | First reactor by 2030, more through 2035 (announced October 2024) |
Constellation notes that restarting a nuclear reactor requires approval from the US Nuclear Regulatory Commission. Google describes its agreement as the world's first corporate agreement to purchase nuclear energy from multiple small modular reactors.
What is not certain
- New reactor designs have yet to be proven at commercial scale in most countries, and schedules for first-of-a-kind projects often move.
- Company timelines are announcements, not guarantees; each project needs regulatory approval.
- Nuclear policy and approvals differ widely by country.
Sources and method
- International Energy Agency, Energy and AI, chapter Energy supply for AI, 2025 (no date shown on the page). https://www.iea.org/reports/energy-and-ai/energy-supply-for-ai
- International Atomic Energy Agency, Small Modular Reactors. Read 29 October 2026. https://www.iaea.org/topics/small-modular-reactors
- Constellation, Constellation to Launch Crane Clean Energy Center, 20 September 2024. https://www.constellationenergy.com/newsroom/2024/Constellation-to-Launch-Crane-Clean-Energy-Center-Restoring-Jobs-and-Carbon-Free-Power-to-The-Grid.html
- Google, New nuclear clean energy agreement with Kairos Power, 14 October 2024. https://blog.google/company-news/outreach-and-initiatives/sustainability/google-kairos-power-nuclear-energy-agreement/
Method: each link was opened on 29 October 2026 and every figure was taken from the page cited beside it. No figure was estimated.
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This article provides general information, not investment advice or an offer of securities.