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South and Central Bulk Planning

Forecasting and Planning

The IESO has launched a South and Central Bulk Planning engagement to actively involve stakeholders and communities in shaping the future of Ontario's transmission system.

The study will build upon the investigations first undertaken through the IESO’s Pathways to Decarbonization study, and later refined through the province’s Powering Ontario’s Growth report, by reviewing the bulk system’s capability to support future generation connections and demand growth in key areas throughout southern and central Ontario. The study will recommend options to enable a future decarbonized power system and support economic growth.

Specific topics include:

  • Confirm the transmission reinforcements required to enable the connection of:
    • The small modular reactor project planned for the existing Darlington nuclear generator station (GS) site, and;
    • The Bruce C project to expanded nuclear at Bruce nuclear GS;
  • Consider the potential for future pumped Storage at Meaford and Marmora
  • Determine the transmission reinforcements that would be required to enable decreased reliance on greenhouse gas emitting resources, specifically:
    • York Energy Centre in York Region
    • Portlands Energy Centre in the city of Toronto
    • Halton Hills GS in GTA West
    • Sithe Goreway GS in GTA West
  • Determine the transmission reinforcements required to enable reliable supply under various long term high growth/ economic development/ electrification scenarios within key growth areas: 
    • Greater Toronto Area
    • Windsor to Hamilton corridor

Actions recommended will focus on early, “no regrets” actions to be taken to address near term needs, while longer term direction will focus on actions to advance or maintain options, including opportunities to preserve new or expanded corridors for future transmission development.

With the formalization of the Bulk System Planning Process in 2022, the IESO seeks to enhance transparency and create opportunities for valuable input from communities and sector participants in individual bulk system studies. By seeking input on the scope of this study, the IESO aims to clarify key issues and strategize an effective engagement approach. Participant involvement during the various phases will ensure views and preferences are considered throughout the planning process. This inclusive approach helps establish a strong foundation for successful implementation, enabling a sustainable plan that can adapt to future demands. The engagement's ultimate purpose is to proactively develop a South and Central bulk transmission plan that fosters reliable electricity supply and supports decarbonization and economic growth objectives, including those set out in the province’s Powering Ontario’s Growth plan. By actively participating in this initiative, sector participants have an opportunity to contribute to a more resilient and prosperous energy future for Ontario. Interested parties are invited to contact the IESO at

Schedule of Activities

Anticipated timing for this engagement is presented below.

Date Engagement Activity Expected Actions

June 19, 2024

Public Engagement Session:

Bulk Transmission Planning Session on 1) South and Central and 2) Northern Ontario bulk studies

This public webinar will provide participants with information about the South and Central and Northern Ontario bulk studies, including its scope, objectives and timeline.


This webinar is being presented during the IESO's June stakeholder engagement sessions, see full agenda for more information.