IESO Releases Transmission Investment Recommendations to Support Growth in Ontario
August 24, 2026
Ontario’s electricity needs are growing and new transmission infrastructure is essential to support economic development, integrate new generation resources, and ensure a reliable electricity system for the future.
The IESO has released three bulk transmission plans covering the east, south and central, and north of Sudbury areas of the province, each recommending a suite of investments to secure Ontario’s energy future. This includes a total of 19 new transmission lines covering roughly 1,850 kilometers, a significant build-out of Ontario’s transmission grid.
These plans are guided by a prudent approach that preserves flexibility and manages risk by recommending certain investments move forward now while others proceed when needed in the future.
North of Sudbury Bulk Plan
In the area north of Sudbury, increasing demand from industrial and mining projects, electrification initiatives, and potential future resource development triggered an assessment of the bulk transmission system. The IESO evaluated transmission needs across the northern network, balancing broader system requirements with regional constraints and interface limitations while facilitating the timely connection of new demand to support growth and economic development. For more information please visit:
North of Sudbury Bulk Plan
North of Sudbury Bulk Plan Backgrounder
South and Central Bulk Plan
The IESO initiated bulk transmission planning for the southern and central regions of Ontario to identify near-term actions and longer-term options to ensure the transmission system can meet forecast demand growth. The IESO also evaluated the grid’s ability to enable the connection of potential future generation resources — including new nuclear — and to reliably supply emerging demand across the Greater Toronto Area and Windsor–Hamilton corridor. As a result, the IESO is recommending a series of investments that will strengthen system resilience and improve reliability — allowing more electricity to flow across the high-voltage grid. To learn more please click:
South and Central Bulk Plan
South and Central Bulk Plan Backgrounder
Eastern Ontario Bulk Plan
With accelerating electricity demand driven by electrification and industrial development, the IESO initiated the Eastern Ontario Bulk Plan to identify near-term actions and longer-term options and ensure the transmission system can reliably support forecasted growth. The recommended transmission upgrades increase the overall transfer capability in eastern Ontario to reliably meet growing needs while creating additional optionality for expanded interties and future exports. For more details please visit:
Eastern Ontario Bulk Plan
Eastern Ontario Bulk Plan Backgrounder
Implementation-ready recommendations are needed by the early- to mid-2030s to improve reliability and support near-term demand growth.
Future-ready recommendations require early development activities, such as preliminary design and environmental approvals, proceeding with construction when system needs and demand growth are confirmed.
Future-consideration recommendations are longer-term opportunities associated with future demand growth, generation development, and evolving policy priorities. These options preserve flexibility to respond to emerging needs without committing to investments before they are required.
Extensive engagement with Indigenous communities, municipalities, industry participants, and stakeholders across Ontario helped shape with plans with several themes emerging consistently: the importance of reliable electricity supply, support for economic growth, and the need for long-term planning certainty.
Together, the IESO’s transmission recommendations provide the foundation for infrastructure needed to support Ontario’s growth, strengthen system reliability, and enable an increasingly electrified future.
The South and Central Bulk Plan
The Eastern Ontario Bulk Plan
The North of Sudbury Bulk Plan
