GTA West
Area Overview
The GTA West region includes the Regional Municipalities of Halton and Peel, and the Municipalities of Brampton, South Caledon, Halton Hills, Mississauga, Milton, Burlington, and Oakville. The GTA West region also encompasses the Northwest Greater Toronto Area sub-region. GTA West and Peel/Halton Region are often used interchangeably throughout electrical studies.
The local distribution companies providing services to customers in the area include:
- Alectra Utilities
- Burlington Hydro Inc.
- Halton Hills Hydro Inc.
- Hydro One Networks Inc.
- Milton Hydro Distribution Inc.
- Oakville Hydro Electricity Distribution Inc.
Community Engagement
The IESO engages with local and regional communities to seek input to help inform planning activities. See Key Resources below for the latest planning documents.
Regional Planning Progress Update
Regional electricity planning has kicked-off in the GTA West electrical region to ensure a reliable supply of electricity, and to support local growth and economic development.
The 2024 GTA West Scoping Assessment Outcome Report has been posted along with the IESO’s response to feedback following the October 29 engagement webinar. The report detailed the need for a coordinated regional planning approach and development of an Integrated Regional Resource Plan (IRRP) for the GTA West electricity region.
Engagement will continue throughout the development of the plan with more details to follow. The GTA West engagement webpage continues to be a source of ongoing information related to regional planning activities, including any upcoming engagement opportunities.
If you would like to learn more about planning activities across the GTA, visit the IESO's Powering the GTA website.
Key Resources
2024 GTA West Scoping Assessment Outcome Report
2024 GTA West Needs Assessment
2021 GTA West Integrated Regional Resource Plan (IRRP)
2019 GTA West Scoping Assessment Outcome Report
2015 Northwest GTA IRRP – Appendices
Related Studies
In 2019, the IESO and the Ministry of Energy and Electrification initiated a joint study to identify land to be protected for a future transmission corridor to support anticipated long-term growth in demand for electricity throughout the province and GTA. This corridor, to be co-located with the proposed Highway 413, will provide regional supply capacity throughout the GTA West and GTA North planning regions, and enhance bulk supply to the GTA.
This initiative will ensure that transmission needs in the area – documented through the regional and bulk planning processes – can be accommodated when they arise. This is part of ongoing efforts to plan today to keep options viable and avoid future unnecessary costs to electricity ratepayers.
With the study currently underway, a Narrowed Area of Interest (NAI) is protected from development while different space requirements and routing options are considered.
Regional planning is currently active in both GTA West and GTA North, and will be coordinated with this corridor study. Bulk system considerations related to this corridor are also being studied through the South & Central Bulk System Study.
This study is separate from, but will continue to be coordinated in parallel with, the Ministry of Transportation’s (MTO) Highway 413 Study.
October 2025 Update:
The Ministry of Energy and Mines (MEM) and the Independent Electricity System Operator (IESO) have reached a milestone in the study and have developed proposed refinements to the Narrowed Area of Interest (NAI). These refinements are based on updated electricity demand forecasts and the latest design work for Highway 413 and are now being shared for public consultation. The proposed refinements would reduce the size of the NAI by approximately 70%, while adding a relatively small area of land to ensure the corridor can support updated electricity system needs in the region and accommodate the updated design of Highway 413 and its auxiliary land uses. The refinements represent the last substantial revision to the study area, to be preserved in the long-term until construction of transmission infrastructure.
Comments and input regarding this proposal are encouraged. A notice was posted on the Environmental Registry of Ontario (ERO) for a 30-day comment period from October 10, 2025 to November 10, 2025. You are welcome to submit comments through the ERO posting.
To contact the project team directly or be added to the mailing list, please e-mail the project inbox: NorthwestGTATransmissionCorridor@ontario.ca.