GTA West

Regional electricity planning in the Greater Toronto Area (GTA) West region is underway to identify the future need of electricity and options to ensure an adequate and reliable supply continues for its residents and businesses.

Community Engagement

The IESO engages with local and regional communities to seek input to help inform planning activities. Learn more about engagement on the current planning cycle.

Area Overview

  • The GTA West Region roughly encompasses the Regional Municipalities of Halton and Peel, and consists of the Municipalities of Brampton, South Caledon, Halton Hills, Mississauga, Milton and Oakville.

The local distribution companies (LDCs) providing service 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.

 The previous planning cycle included the following IESO activities:

  • Release of an Integrated Regional Resource Plan (IRRP) for the GTA West Northern sub-region (“Northwest GTA”) in April 2015, followed by the publication of a Regional Infrastructure Plan (RIP) in January 2016
  • Completion of a Scoping Assessment for the GTA West Southern sub-region in September 2014 that concluded needs would be addressed through local coordination between the transmitter and LDC(s)

Previous cycle regional planning activities

The Northwest GTA sub-region was the focus of the previous planning cycle due to the high load growth, expanding urban boundaries, limited existing electrical infrastructure, and the requirement for coordination with bulk system plans.

Northwest GTA sub-region

The last regional planning process cycle for the Northwest GTA sub-region was completed in April 2015 and an Integrated Regional Resource Plan (IRRP) was released, which identified the following:

  • Near-term need for two new step-down transmission facilities to ensure new customer connections can be accommodated in Halton Hills and Milton
  • Medium-term need for a transmission line upgrade to address emerging capacity needs in the central Brampton area
  • Long-term need to provide additional transformer and transmission line capacity in Northern Brampton/Southern Caledon and Halton Hills to meet forecast demand growth

Key Resources

Related Studies

The IESO and the Ministry of Energy, Northern Development and Mines have 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 in the GTA West region. Part of ongoing efforts to plan today to avoid future costs to electricity ratepayers, this initiative will ensure that transmission needs – documented through the regional planning process – in the study area (see map below) can be accommodated if and when they arise.

Although the area of study is primarily centered in the GTA West planning region, parts extend into GTA North (see map below). This study will proceed in parallel with the resumption of the Greater Toronto Area West Highway Corridor Environmental Assessment study conducted by the Ministry of Transportation.

More information on the study, along with related engagement opportunities, will be available shortly. For further information, email

Note: The Ministry of Transportation and the IESO will no longer proceed with the Northwest GTA Corridor Identification multi-purpose linear infrastructure study.

GTA West