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Darlington Refurbishment Project Delivered Ahead of Schedule and Under Budget

February 9, 2026

OPG has announced a significant milestone with the completion of construction on the refurbishment of the Darlington Unit 4 nuclear reactor.

The unit is now complete and will be returning to service four months ahead of schedule, the overall refurbishment project coming in $150 million under budget. Originally expected to return to power in August 2026, the unit has received approval from the Canadian Nuclear Safety Commission to enter the initial power testing, which is expected to begin on February 12, and will be at full power shortly after. Refurbishment and continued operations over the next 30 years at Darlington is expected to generate up to $90 billion in economic benefits for Ontario, support approximately 14,200 jobs and produce enough clean electricity to power 3.5 million homes.



“Darlington Unit 4’s early return to service is great news for Ontario. Nuclear generation is a critical part of Ontario’s diverse electricity supply mix, and this facility’s early return means it will be available to help keep our grid reliable for Ontarians during the summer when demand is at its highest. We are proud that the IESO’s Operations team was able to support today’s announcement by working in close collaboration with OPG and the Ontario government as they complete another refurbishment project ahead of schedule and under budget,” commented Lesley Gallinger, President and CEO, Independent Electricity System Operator

The Darlington refurbishment project involved the complete overhaul of all four nuclear reactor units, extending the station’s operating life to at least 2055. With all four units refurbished and ready to be brought back online, this marks the completion of the world’s largest refurbishment project to-date, with the Darlington Nuclear Generating Station ready to deliver more than 3,500 megawatts (MW) of clean, reliable, emission-free electricity — enough to power 3.5 million homes — for at least 30 more years.

The Darlington refurbishment project was completed by over 6,000 Ontario workers, including skilled tradespeople, support services workers and project managers. Refurbishment work included replacing thousands of fuel channels, feeder tubes, calandria tubes, and end fittings, as well as rehabilitating other critical components. The project also included system improvements and plant upgrades to meet current regulatory requirements. During the construction phase, the project contributed an estimated $14.9 billion to Ontario’s GDP, with 96 per cent of project spending retained in the province. For every dollar invested, Ontario’s GDP increased by an average of $1.30, ensuring Ontario dollars continued to support local workers, families, and businesses at home.

Nuclear energy remains the backbone of Ontario’s clean electricity grid, providing the clean, reliable and affordable power needed to support new housing, advanced manufacturing and growing communities. As a global nuclear leader, Ontario is home to the first grid-scale small modular reactor (SMR) under construction in the G7, as well as three nuclear generating stations, with a track record of delivering multiple large-scale refurbishments on-time and on-budget.

“Bringing the Darlington refurbishment in ahead of schedule and under budget will clearly demonstrate our team’s ability to deliver large and complex nuclear projects,” said Nicolle Butcher, President and CEO, Ontario Power Generation. “The skills we developed and lessons we learned during this project are invaluable as we proceed with refurbishing Pickering Nuclear Generating Station, continue construction on the G7’s first Small Modular Reactor at the Darlington New Nuclear Project, and study the potential for up to 10,000 MW of new nuclear at Wesleyville.”

Refurbishing the Darlington Nuclear Generating Station is a key pillar of Energy for Generations, the province’s first-ever integrated energy plan to power a resilient, self-reliant and competitive economy. The government’s integrated approach and record investments in energy infrastructure are also providing the certainty needed for Indigenous communities, municipalities, businesses and industry partners to invest confidently in Ontario’s future. With a clear path forward, the plan is not only meeting the demands of today, but also protecting jobs, supporting workers and powering economic growth for generations to come.

“OPG’s completion of Darlington Unit 4 ahead of schedule and under budget is a strong example of what disciplined execution can deliver—grounded in decades of refurbishment experience, a coordinated supply chain, and a highly skilled workforce. This achievement also signals that OPG has the leadership and delivery capability to build the first Small Modular Reactor in the G7, applying the same rigorous commitment to safety, quality, and reliability throughout its development. GE Vernova Hitachi is proud to be collaborating with OPG to deploy our BWRX-300 technology at Darlington, and we’re optimistic about what we can deliver together for communities and the broader energy system,” commented Lisa McBride, Country Leader, Small Modular Reactors, GE Vernova Hitachi.

Quick Facts

  • Nuclear power currently provides about 50 per cent of Ontario’s electricity supply and has positioned Ontario as one of the cleanest electricity grids in the world.
  • According to Ontario’s Independent Electricity System Operator (IESO), the province’s demand for electricity is forecast to increase significantly by 2050.
  • The Darlington refurbishment project was completed by over 6,000 Ontario workers over the course of the project, including members of:
    • Society of United Professionals
    • Power Workers’ Union
    • Canadian Union of Skilled Workers
    • Electrical Power Systems Construction Association
    • United Association
    • International Brotherhood of Electrical Workers
    • Ironworkers/Rodmen
    • Millwrights
    • Boilermakers
    • Carpenters
    • Labourers
    • Sheet Metal/Roofers
    • Operating Engineers
    • Cement Masons
    • Painters
    • Plasterers
    • Teamsters
    • Brick and Allied Craft Union/Tile & Terrazzo
  • OPG captured approximately 8,000 lessons learned over the course of the project that were applied throughout the refurbishment to save time and money, which will benefit other large nuclear projects, including the Pickering Nuclear Generating Station Refurbishment Project, refurbishment and new build at the Bruce Nuclear Generating Station, and construction of the first small modular reactor (SMR) in the G7 at the Darlington site.
  • In September 2025, the Canadian Nuclear Safety Commission (CNSC) granted OPG a 20-year licence for the Darlington Nuclear Generating Station, authorizing OPG to operate the station until November 30, 2045, which is the longest nuclear operating licence granted to date in Canada.

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