The Ontario government has announced plans to reduce the boundaries of the corridor it needs to build the Northwest GTA Transmission Line by as much as 40 percent.

The news comes as part of its Northwest GTA Transmission Corridor Identification Study. The study looked at the lands required to build the line, including for transmission and highway corridors.

The transmission corridor itself will host major infrastructure projects that will support the government’s long-term plan to deliver reliable, affordable and secure energy.

"As Ontario’s population and economy continue to grow in the GTHA, we are planning ahead and building for future generations,” said Energy Minister Stephen Lecce. “This milestone reflects our government’s commitment to deliver reliable, cost-effective energy infrastructure that meets growing energy demand, while keeping energy affordable for families.”

Halton, Peel and York are among the fastest-growing regions in Ontario, with electricity demand far exceeding the provincial average. As communities expand further from existing transmission infrastructure, the Independent Electricity System Operator (IESO) has confirmed the need for new transmission capacity to bring electricity into and throughout Northwestern GTA.

The proposed corridor along Highway 413 is based on a study launched in 2019 to identify a viable route for future transmission infrastructure. The refined corridor reflects detailed technical analysis to identify the narrowest path capable of supporting both 230 kV and 500 kV transmission lines, while preserving flexibility for future transmission designs. The study prioritized co-location with Highway 413, minimizing impacts on natural areas, and avoiding built-up communities.

“Aligning the Northwest GTA Transmission Corridor with Highway 413 means we're keeping Ontarians moving while meeting electricity demand for generations to come,” said Transportation Minister Prabmeet Sarkaria.

Throughout the process, municipalities, stakeholders and Indigenous communities have been engaged at key milestones to inform and shape the proposal. The proposal and updated maps are now available for public comment on the Environmental Registry of Ontario. The Ministry of Energy and Mines and the Ministry of Transportation are expected to announce their finalized land use plans and release surplus lands in December 2025.

Concurrent with the consultation, the provincial transport ministry is preparing to finalize the route alignment for Highway 413.