Enhancing Transmission Capacity East of Toronto - The Bowmanville to Greater Toronto Area (GTA) Transmission Line

ERO number
025-0658
Notice type
Policy
Act
Ontario Energy Board Act, 1998
Posted by
Ministry of Energy and Mines
Notice stage
Proposal
Proposal posted
Comment period
June 16, 2025 - August 15, 2025 (60 days) Open
Last updated

This consultation closes at 11:59 p.m. on:
August 15, 2025

Proposal summary

We are proposing actions to facilitate the development of a critical transmission project to alleviate system constraints east of Toronto, supporting demand growth in the GTA and new generation east of Toronto, while also advancing a shared goal of reconciliation by providing economic and partnership opportunities for Indigenous communities.

Proposal details

The Government of Ontario has recently issued and published its Integrated Energy Plan, Energy For Generations: Ontario’s Integrated Plan to Power the Strongest Economy in the G7 (the Plan), which outlines the actions being proposed or taken by the provincial government to meet the challenge of generating and delivering the affordable, secure, reliable and clean, energy Ontarians need. The Plan highlights electricity transmission projects that should proceed with early planning and development work to alleviate existing transmission bottlenecks identified by the Independent Electricity System Operator (IESO) in their ongoing regional and bulk planning studies, including the Central Ontario Bulk Plan Study, currently underway.

Consistent with this plan, and based on recommendations of the IESO, the Ministry of Energy and Mines (ministry) is proposing to take actions to facilitate the development of:

  • A double-circuit 500-kilovolt (kV) transmission line that will run from an expanded Bowmanville Switching Station (SS) in Bowmanville, that is being developed and constructed by Hydro One to enable connection of the four new Small Modular Reactors, to a new or existing station in the GTA, and associated station facilities. The termination point will be in accordance with the recommendations of the IESO, which will be determined with the release of the South and Central Ontario Bulk Plan study in Q3 2025.

The proposed actions, subject to fulfillment of all applicable consultation obligations, including the Crown’s Duty to Consult, and receiving all required approvals, are intended to:

  • Support the planned transmission project so that it may be built on time and cost-effectively to enable new clean generation connections east of Toronto and meet future demand growth in Toronto and the GTA.
  • Advance a shared goal of reconciliation with Indigenous communities by enabling economic, partnership, and leadership opportunities that can bring prosperity and security to the region.

The IESO’s Central Ontario Bulk Plan Study, which commenced in 2024, has confirmed the need for this new transmission project to enable the connection, subject to relevant approvals, of the second of four proposed Small Modular Reactors (SMRs) at the Darlington Nuclear Generating Station and supports demand growth in Toronto and the GTA. This need was previously communicated through the IESO’s February 8, 2024, report titled “Connection Approach to Small Modular Reactors at the Darlington Nuclear GS.” The IESO will determine the transmission project’s preferred termination point within the GTA area as they proceed with the bulk study, which is anticipated to conclude by Q3 2025.

Our proposed actions for public feedback are as follows:

1. Prioritize the Bowmanville to the GTA Transmission Line

The ministry is proposing to bring forward an Order in Council that would, subject to fulfillment of all applicable consultation obligations, including the Crown’s Duty to Consult and receiving all required approvals, declare the following transmission project, recommended to be in-service by the early 2030s, to be a priority project under section 96.1 (1) of the Ontario Energy Board Act, 1998 (OEBA):

  • A double-circuit 500-kilovolt transmission line that will run from an expanded Bowmanville SS in Bowmanville, that is being developed and constructed by Hydro One to enable connection of the four new Small Modular Reactors, to a new or existing station in the GTA, and associated station facilities.

Per section 96.1 (2) of the OEBA, this declaration would require the Ontario Energy Board (OEB), the provincial economic regulator of the energy sector, to accept that this line is needed when assessing whether the project is in the public interest as part of its Leave to Construct review process. This would streamline the OEB’s review and prevent delays to ensure that the project is brought online on time. The OEB would still be required to consider the interests of electricity consumers with respect to project costs and the reliability and quality of electricity service.

Declaring this transmission line to be a priority project would not impact the requirement for the transmitter to obtain all required government approvals, including under the Environmental Assessment Act and obtaining Leave to Construct from the OEB. These approvals include requirements for the transmitter to consult with the public, stakeholders and potentially impacted Indigenous communities on the proposed project.

2. Designate Hydro One as Transmitter

The ministry is also proposing, subject to fulfillment of all applicable consultation obligations, including the Crown’s Duty to Consult and receiving all required approvals, to direct the OEB, pursuant to section 28.6.1 of the OEBA, to amend Hydro One Networks Incorporated (Hydro One)’s transmitter licence to require it to undertake development work and seek all necessary approvals to construct the transmission project listed above.

The IESO stated that this project is needed on an urgent basis and leverages existing infrastructure and corridors, therefore indicating that it is not suitable for competitive procurement. By designating Hydro One, the ministry would be providing the regulatory clarity to initiate project development work and advance Indigenous partnership discussions on this project. This would help to avoid the possibility of delays in the approvals process which can add to development timelines and increased costs that are ultimately borne by electricity ratepayers.

As the local transmitter in the region, Hydro One is best situated to promptly undertake development work for this project. Hydro One’s ownership of the connecting infrastructure and transmission along the existing corridor better enables them to site new transmission in a location where corridor expansion is limited. Additionally, Hydro One is familiar with Ontario’s regulatory and permitting processes and has established relationships with local and Indigenous communities. All these factors best position Hydro One to advance the development of this project. Furthermore, Hydro One’s First Nation Equity Partnership Model, launched in 2022, offers First Nations the opportunity to advance the project together in partnership and a 50% equity stake in new transmission lines exceeding $100 million. This model is expected to advance reconciliation by creating economic opportunities for First Nation communities, such as equity participation, procurement opportunities, and jobs.

Consultation with Indigenous Communities on this Proposal:

The provincial Crown is committed to fulfilling its duty to consult with Indigenous communities in respect of its conduct that may have the potential to adversely impact Aboriginal and treaty rights protected under Section 35 of Canada’s Constitution Act, 1982 (section 35 rights). The ministry will provide information about the proposed transmission project and the above policy actions to potentially impacted Indigenous communities, including information about how they can participate in the consultation process at this early stage of project development.

This would include an opportunity to review and provide comments about this proposal through the Environmental Registry of Ontario (ERO), as well as targeted consultation opportunities for potentially impacted Indigenous communities to share their input about the proposed action and any potential for impacts to section 35 rights directly with ministry staff.

In addition, should the proposal move forward, the province expects to delegate the procedural aspects of Crown consultation to the transmitter in respect of the transmission line, which may be fulfilled through the Ministry of Environment, Conservation, and Parks’ (MECP) environmental approvals and other provincial regulatory approvals and permits as appropriate.

Timing:

Depending on the outcomes of consultation, including consultation with Indigenous communities, the ministry anticipates bringing this proposal forward for a possible decision in later in 2025, to ensure the transmission line identified above can meet the IESO‘s recommended in-service date.

Environmental Impact:

Like all infrastructure projects, transmission projects have the potential to impact land (e.g., impacts to farmland), local environments and ecosystems, such as watersheds. These proposed actions do not impact the requirement for the transmitter to obtain all required government permits and approvals, including those required under the Environmental Assessment Act, prior to proceeding with the project’s construction. These approvals include requirements for the transmitter to consult with Indigenous communities, the public, and stakeholders on the proposed project, including in the determination of the exact path of the line, its impacts to the environment, and any appropriate mitigation measures.

Building transmission infrastructure is essential for maintaining Ontario’s affordable, secure, reliable and clean energy advantage. Success in achieving these objectives could have significant positive impacts on the environment.

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Contact

Cisca McInnis

Email address
Office
Ministry of Energy and Mines
Address

77 Grenville Street
Toronto, ON
M7A 2C1
Canada

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Contact

Cisca McInnis

Email address
Office
Ministry of Energy and Mines
Address

77 Grenville Street
Toronto, ON
M7A 2C1
Canada

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