Friday, January 9, 2026
The Government of Ontario announced it has approved the Independent Electricity System Operator’s (IESO) recommendation to build a new underwater electricity transmission line from near the Darlington Nuclear Generating Station to the downtown core and eastern portion of the City of Toronto.
This first-of-its-kind high-voltage underwater transmission line in Ontario will deliver up to 900 megawatts (MW) of clean, reliable power. According to the province, the project aligns with Ontario’s investments to upgrade and expand nuclear generating capacity on-time and on-budget, including the Darlington Nuclear Refurbishment Project and the construction of the first small modular reactors in the G7 at Darlington New Nuclear Project.
“As we start 2026, we are focused on strengthening Ontario’s economy and creating jobs,” said Stephen Lecce, Minister of Energy and Mines. “Without a new transmission line, Toronto would have to turn down job-creating investments and reduce housing, which is simply unacceptable. We are thinking ahead and building for the future by approving a new transmission line that will enable 285,000 new homes, power new businesses, and create thousands of jobs. We are also initiating the first IESO-led competitive transmission procurement to reduce costs and maximize benefits for families.”
As Toronto’s electricity system approaches its capacity limit, at the same time the city is experiencing unprecedented growth, with the highest demand in the downtown core. Currently, the City of Toronto is supplied by two transmission lines, one from the west at Manby Transmission Station (TS) and one from the east at Leaside TS. These pathways will begin to reach their capacity in the 2030s, demonstrating a clear need for additional transmission infrastructure.
“Toronto is the fastest-growing city in North America, and that growth means we need more power to fuel our homes, transit, and businesses,” said Olivia Chow, Mayor of Toronto. “I want to applaud the Ontario government for moving forward with this first-of-its-kind underwater transmission line. It’s an exciting example of the province and city working together to build resilient, clean energy infrastructure that keeps costs down, supports good-paying jobs, and powers the projects that will shape Toronto’s future. We’re committed to creating an affordable and caring city that delivers for Torontonians.”
To keep costs affordable, the government is proposing the IESO launch a competitive procurement process to select a transmitter, which will be informed by a consultation on the procurement design. This approach will drive value for ratepayers while accelerating construction and creating opportunities for Indigenous participation and good-paying jobs across the province.
“Toronto’s demand for electricity is increasing significantly. A new underwater transmission line into Toronto will ensure electricity remains reliable for residents and businesses while enabling economic growth. The IESO has engaged with transmitters, Indigenous communities and other interested stakeholders to inform our recommendation for the underwater line which will be procured through a competitive process. This approach will ensure we provide the best value to ratepayers while supplying Toronto’s energy needs for generations to come.” said Lesley Gallinger, president and CEO, IESO.
An underwater third transmission line will build system resilience by providing an option that is less vulnerable to extreme weather events such as flooding or ice storms, instances that have previously resulted in lost electricity supply and $100–200 million in costs and lost productivity. The underwater cable will also deliver more capacity than any other option and meet the system needs beyond 2044, reducing the need for additional, costly upgrades and expansions. The third line will also alleviate strain on the bulk power system by avoiding bulk system reinforcements elsewhere in the GTA which could result in an estimated preliminary savings of $100–$300 million.
“As Toronto’s energy needs expand, strengthening our city’s access to safe, reliable and resilient electricity is essential to supporting our shared future and fostering growth opportunities in our community and economy. Toronto Hydro is supportive of the ongoing development of the Third Line, and today’s update from the Province marks an important moment in growing the connection between our provincial energy system and the local homes and businesses that rely on it. By expanding our region’s transmission capacity, we’re investing in a bright, sustainable future for all Torontonians,” said Jana Mosley, president and CEO, Toronto Hydro Corporation.
The development, construction and commissioning of a third transmission line to Toronto could take between seven to 10 years to complete,
Featured image: (Government of Ontario)
