Ontario Focused on Economy by Approving New Toronto Transmission Line

Province launches first IESO-led competitive transmission selection process to maximize benefits

The Ontario government is starting 2026 with a focus on driving growth and creating jobs by approving 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 ensures the province will keep up with growth as electricity demand in Toronto is expected to double by 2050. Ontario’s plan will deliver up to 900 megawatts (MW) of clean, reliable power, securing the electricity needed to fuel housing, transit, and economic growth. This project aligns with Ontario’s record 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. Ontario’s plan to build a third transmission line will meet growing demand by delivering 900 MW of additional power, equivalent to all the power generated from three small modular reactors, or power for 900,000 new homes.

“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.

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.

The development, construction and commissioning of a third transmission line to Toronto could take between seven to 10 years to complete, underscoring the importance of acting now to further Ontario’s clean energy advantage, ensure reliability and position the province and city to put shovels in the ground sooner on critical infrastructure projects. The IESO’s recommendation follows extensive technical analysis of multiple options, prioritizing routes that minimize land-use impacts by leveraging existing corridors, underground infrastructure and pathways. The proposal is detailed in the 2025 Toronto Integrated Regional Resource Plan.

Expanding transmission infrastructure is a key pillar of Energy for Generations, the province’s first-ever integrated energy plan to ensure Ontario has the reliable, affordable power it needs to power new homes and drive economic growth. The government’s integrated approach and record investments in energy infrastructure are 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 it is protecting jobs, supporting workers and powering economic growth for generations to come.

Quick Facts

• High-voltage underwater transmission lines have been used in other Canadian jurisdictions such as Newfoundland and Labrador, Nova Scotia, and Prince Edward Island.
• 900 MW is equivalent to powering 900,000 homes.
• Peak electricity demand in Toronto is 4,700 megawatts, which is approximately 20 per cent of peak demand for all of Ontario. According to Ontario’s Independent Electricity System Operator, after 20 years of flat electricity demand in the city, Toronto’s peak demand is expected to roughly double by 2050, which includes:
  • Building New Homes: Energy to power at least 285,000 new homes in Toronto as part of the city’s 10-year housing target. That includes new communities at Downsview, Port Lands, East Harbour and Golden Mile.
  • Economic growth: Toronto is an attractive investment destination and serves as a provincially and nationally significant centre for job creation and economic growth.
  • Transit expansion: GO Transit Electrification and the new Ontario Line alone are anticipated to add an additional 100 megawatts of energy demand to Toronto’s system.
  • Electrification: Increased adoption of electric vehicles.
• The Integrated Regional Resource Plan (IRRP) for Toronto, developed by the IESO, is part of a broader effort to anticipate and plan for localized electricity needs across Ontario.