Ontario Construction News staff writer
The Ontario government and the City of Toronto are moving forward with plans to build a third electricity transmission line into the downtown core, aiming to support major infrastructure projects, future housing developments, and economic growth as energy demand continues to rise.
“As we build more housing, transit and create more jobs, we’re going to need the power that fuels and sustains economic growth,” said Toronto Mayor Olivia Chow in a statement. “We’re ready to work with the provincial government to advance a third transmission line that will help power our growing city.”
The new line is being proposed as electricity demand in Toronto is expected to nearly double by 2050, driven by development in areas like the Port Lands and East Harbour and by large-scale transit projects such as the Ontario Line. The Independent Electricity System Operator (IESO) has confirmed a third supply route will be required, as the city’s two current transmission lines — from Manby Transmission Station in the west and Leaside Station in the east — are projected to reach capacity by the early 2030s.
“We are acting now to protect Ontario families, workers and businesses by ensuring our province’s largest city has the power it needs to grow,” said Stephen Lecce, Minister of Energy and Mines. “This infrastructure will support new communities and major projects while ensuring a reliable and affordable energy supply without relying on other jurisdictions.”
The IESO has identified three preliminary options for the new line, all designed to minimize land-use impacts through the use of existing transmission corridors or alternative routes:
An overland line from Pickering to Leaside via Cherrywood Transmission Station;
A mixed overland and underground line from Pickering to the Port Lands, connecting Cherrywood to Hearn Station via Warden Station;
An underwater cable running through Lake Ontario from Darlington or Pickering to the Port Lands.
Public and stakeholder consultation will continue this summer, including engagement with Indigenous communities, the City of Toronto and affected stakeholders. The IESO is expected to deliver a final recommendation by the end of August 2025.
Depending on the selected route and required approvals, construction could take between seven to 10 years, making early planning critical to avoiding delays in supporting housing and infrastructure timelines.
The third transmission line is part of a push to expand energy infrastructure through its upcoming Integrated Energy Plan, expected to be released later this month. That strategy aims to enhance the province’s competitiveness, attract investment and reduce reliance on natural gas generation.
In addition to the new line, the IESO will explore complementary solutions, such as rooftop solar, battery storage, and expanded energy efficiency programs, to reduce peak demand and strengthen system resilience.
“This is about securing Ontario’s clean energy advantage,” Lecce said. “We’re ensuring our province is the most competitive place to invest and create jobs in the G7.”
