Darlington nuclear power generating station in Ontario, Canada, is one of North America’s most important nuclear energy hubs and is currently undergoing a major modernization and expansion phase as part of the New Nuclear Project that positions it at the center of Canada’s long-term clean-power strategy. As of early 2026, the station’s multi-billion-dollar refurbishment program is nearing completion with three of four reactor overhauls finished. The final unit is expected back online end of February 2026. Construction has also begun on the first of four planned small modular reactors (SMRs) after federal regulators granted a license in 2025.

Additionally, Ontario is investing heavily in surrounding infrastructure. This includes new transmission capacity from the Darlington area to Toronto to meet demand expected to double by 2050. Ontario is also at the center of another mega development poised to become the largest nuclear power station in the world at Port Hope municipality.

Darlington Nuclear Power Generating Station Project Overview

Location: Clarington, Ontario, Canada

Owner/Operator: Ontario Power Generation (OPG)

Facility type: Nuclear generating station (CANDU PHWR reactors)

Units: 4 reactors

Output per unit: 878 MW

Total station capacity: 3,512 M

Refurbishment program value: C$12.8 billion (US$9.4 billion)

Refurbishment execution phase: 2017–2026

Economic impact: C$90 billion benefit to Ontario

Latest Project Status as of 2026

Construction work on the full refurbishment program was completed in early 2026, with final testing underway on Unit 4 before commercial return to service.

• Unit 2 returned to service: June 2020
• Unit 3 returned to service: July 2023
• Unit 1 returned to service: November 2024
• Unit 4 completion: 2026

The refurbishment adds about 30 years of operating life, extending plant operation toward the mid-2050s.

SMR Expansion Program

Regulator granted license to construct first SMR in 2025

Planned reactor type: BWRX-300 (300 MW each)

Planned number of SMRs: 4

Total SMR capacity: 1,200 MW

Target completion of first SMR: by end of decade

Darlington produces roughly 15 percent of Ontario’s electricity when three units are operating.

Factsheet for Darlington New Nuclear Project

Site: Darlington Nuclear Generating Station

Country: Canada

Owner/operator: Ontario Power Generation

Reactors: 4 CANDU units

Capacity: 3,512 MW total

Refurbishment cost: C$12.8 billion

Refurbishment duration: 10 years

Completion: 2026

Lifetime extension: Plus 30 years

SMR expansion: 4, 300 MW units planned

Project Contractors and Stakeholders

Ontario Power Generation as owner/operator

Canadian Nuclear Safety Commission as regulator, licensing authority

Candu Energy (AtkinsRéalis company) as SMR execution contractor

GE Power as generator supplier

Construction to Begin on First SMR at Darlington New Nuclear Project Site in Ontario, Ontario

Reported May 9, 2025 – Construction has begun on the first of four small nuclear reactors (SMR) at Darlington nuclear power generating station in Ontario, Canada.  Estimated to cost US$4.38 billion, the reactor is located on a nuclear site in Clarington, Ontario and is part of the larger, US$15 billion Darlington New Nuclear Project.

Additionally, the small modular reactor, BWRX-300 is expected to generate enough clean electricity to over 300,000 homes. Commercially available uranium will be used on site to generate the energy. This plant is the first in the G7 to be deployed at the site. Ontario Power Generation expects that the project will reach commercial operation by 2030.

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Site preparation for the Darlington nuclear power generating station began in December 2022. The license to construct the unit was awarded by the Canadian Nuclear Safety Commission in April 2025. Over 80 companies in the province have signed agreements with Ontario Power Generation to deliver this project.

Also involved in the project are Kiewit Nuclear Canada and Aecon who have signed a US$1.3 billion construction contract for the execution phase of the nuclear project. The partnership will be also working with GE Vernova Hitachi Nuclear Energy and AtkinsRéalis to deliver the Darlington nuclear power generating station. 

Project Overview

Location: Clarington, Ontario

Project cost: US$15 billion

Nuclear reactor model: BWRX-300

Commercial operation date: 2030

Developers: Kiewit Nuclear Canada, Aecon, GE Vernova Hitachi Nuclear Energy, AtkinsRéalis

Benefits of the SMRs at Darlington Nuclear Power Generating Station in Ontario, Canada

In addition to the 300,000 homes supplied with energy from the project, Canadians will benefit from 18,000 jobs created directly and indirectly through the project. Additionally, $500 million is expected to be injected into the economy annually thanks to this project. In total, CAD$38.5 billion will be added to the country’s GDP over the next 6 years during the construction, operation and maintenance of Darlington nuclear power generating station. Compared with other non-emitting generation alternatives, the Independent Electricity System Operator (IESO) has also identified the Darlington New Nuclear Project as the most cost-effective and least risky option, for meeting the growing electricity demand, which is set to increase by 75% by 2050.

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