Ontario Approves Construction of Small Modular Reactor at Darlington Site in Clarington
Ontario Power Generation (OPG) has received approval from the Ontario government to begin construction on the first of four small modular reactors (SMRs) at the Darlington nuclear site in Clarington, according to a provincial government news release dated May 8, 2025. The government states this will be the first small modular reactor built in a G7 nation. Once all four reactors are complete, they are expected to supply up to 1,200 megawatts of electricity, which the government reports is enough to power approximately 1.2 million homes.
The Ontario government describes this project as a response to anticipated increases in provincial electricity demand, which it expects will rise by at least 75 percent by 2050. The government projects up to 18,000 Canadian jobs could be created during construction and approximately 3,700 jobs sustained during ongoing operations and maintenance. According to the news release, about 80 percent of project spending is anticipated to go to Ontario companies, and more than eighty Ontario-based companies have already signed agreements with OPG to participate in the project.
According to the news release, government estimates put the cost of the first SMR at $6.1 billion, with an additional $1.6 billion budgeted for systems and services common to all four reactors. The Ministry of Energy and Mines states that costs are expected to decrease with each additional reactor as construction progresses. The reactors, identified as BWRX-300 units, will use commercially available uranium as their fuel source.
Ontario's Independent Electricity System Operator (IESO) concluded that building the new SMRs at Darlington is the preferred option to meet the province’s future energy demand when compared with other non-emitting power generation alternatives, according to the government announcement. The release also notes that, according to IESO, replacing the four SMRs’ output with wind, solar, and batteries would require significant land and transmission infrastructure.
Site preparation for the first SMR began in December 2022, with planning and licensing for the remaining three starting in July 2023, as detailed in the government statement. The Canadian Nuclear Safety Commission granted OPG a licence to construct the first SMR in April 2025, according to the release.
The provincial government reports it is exploring financial arrangements to help limit potential costs for electricity ratepayers. In parallel, OPG is assessing additional financing options. OPG is also continuing to develop relationships with the Williams Treaties First Nations and is pursuing possible equity partnerships for these communities, which the government states would be a first-of-its-kind partnership in Canada for nuclear energy generation.
In addition to local partnerships, the Ontario government and OPG are collaborating with power authorities in Alberta, Saskatchewan, and New Brunswick on small modular reactor development, according to the announcement. Several Ontario officials and local leaders are quoted in the release, including Clarington Mayor Adrian Foster, who referenced expectations for increased employment and local economic activity during both construction and operation of the project.