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yesterday

Ontario Approves Underwater Power Line to Toronto to Deliver 900 MW From Darlington

An IESO-run competition this year will choose a builder, with construction slated to start next year, targeting a latest in-service date of 2037.

Stephen Lecce, minister of energy and mines of Ontario, speaks at a press conference as Ontario Premier Doug Ford looks on, in Toronto on Thursday, April 17, 2025.
Darlington Nuclear Generating Station in Clarington, Ont., in March, 2025. The Ontario government has approved construction of a new underwater electricity line Wednesday that would run along the bottom of Lake Ontario from the station to Toronto.

Overview

  • The Third Line would run roughly 65 kilometres under Lake Ontario from the Darlington Nuclear Generating Station to a terminal station in Toronto’s Port Lands.
  • Ontario pegs the project at about $1.5 billion based on a high-level estimate, with a possible range from $750 million to $3 billion.
  • The government says it will launch the first IESO-led competitive transmission procurement this year to select a transmitter and drive cost discipline.
  • Officials cite sharply rising Toronto demand and limited capacity on existing corridors in the 2030s, arguing the subsea route provides greater capacity and resilience to extreme weather than overland options.
  • The 900‑megawatt link is expected to reduce Toronto’s local reliance on the Portlands gas plant, though the IESO notes the facility may still be required for provincial peak reliability, and city leaders and Toronto Hydro have endorsed the plan.