Ontario’s $9.8B Transmission Plan Targets Toronto Grid Bottleneck

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Ontario’s electrical energy system operator is getting ready for a step-change in grid capability as demand is projected to rise almost 65% by 2050, with peak load growing from roughly 23–24 GW at present to as excessive as 40 GW in high-demand eventualities, based on the Impartial Electrical energy System Operator 2026 Annual Planning Outlook.

Planning fashions present probably the most acute will increase are concentrated in southern Ontario, significantly within the Higher Toronto space, the place electrification of buildings, transportation and business is driving sustained peak demand development.

Particular person giant hundreds are amplifying that stress. Knowledge facilities and electrified industrial amenities can add a number of hundred megawatts at a time, creating localized spikes that current transmission infrastructure can’t take in.

Ontario expects 16 extra information facilities to hook up with its grid over the following decade, representing 13% of latest electrical energy demand and 4% of complete anticipated demand, based on evaluation revealed in Energy Regulation Quarterly.

Toronto-Sure Energy Flows Hit Switch Limits

The system operator’s reliability framework identifies transmission—not era—because the binding constraint. The first hall delivering energy into the Toronto space, often called the Move East In direction of Toronto interface, has a switch functionality of about 5,900 MW, based on the grid operator’s planning information.

Planning supplies establish this interface as a constraint throughout summer season peak demand durations, when excessive temperatures scale back line scores and demand is elevated, with limits typically set by 230-kV circuits between Trafalgar Transmission Station in Oakville, about 24 miles west of Toronto, and Richview Transformer Station in Toronto’s west finish.

On the similar time, energy from the Bruce nuclear complicated should transfer by means of west-to-east interfaces with switch capabilities exceeding 5,600 MW, concentrating era flows towards the identical constrained Toronto-bound hall.

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Peak demand approaching 40 GW means the roughly 5,900-MW switch functionality into the Toronto area should serve a rising share of system load, requiring a number of thousand megawatts of further switch capability underneath higher-demand eventualities to keep up reliability margins.

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IESO offered draft suggestions throughout an April 30 engagement session, choosing Portfolio B with an upfront capital price of $9.8 billion, in contrast with alternate options priced at $9.2 billion and $9.3 billion, respectively.

The operator cited Portfolio B’s main efficiency on reliability, operability, resilience and broader system advantages as the idea for the choice. A last report is predicted in mid-2026. ENR reached out to IESO for remark however didn’t obtain a direct response.

IESO’s draft planning supplies define a buildout anchored by a number of high-voltage transmission corridors linking main era sources to the Higher Toronto Space. Draft portfolios embody double-circuit 500-kV traces extending roughly 140 km and 190 km from the Bruce nuclear complicated into central Ontario and the Higher Toronto Space, together with a 60-km 500-kV reinforcement feeding into the northwest Toronto space.

Further reinforcements embody a 50-km double-circuit 500-kV line east of Toronto and a roughly 70-km high-voltage direct present line delivering energy straight into the town’s Hearn station, supported by converter amenities.

The plans additionally name for expanded 500/230-kV autotransformer stations and related substation infrastructure, together with breakers, buswork and reactive gear to handle elevated energy flows.

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IESO’s planning course of explains why a definitive undertaking record has not but been revealed. In its materials, the operator states that the majority system planning course of evaluates a number of infrastructure portfolios throughout demand eventualities to check system efficiency underneath totally different circumstances.

IESO chart comparing transmission portfolios and performance criteria

IESO evaluated three transmission portfolios throughout six efficiency standards earlier than choosing Portfolio B—the highest-cost possibility at $9.8 billion—at its April 30 South and Central Bulk Plan engagement session. The operator cited Portfolio B’s main scores on reliability, operability, resilience and system advantages as the idea for the advice. Click on to enlarge picture.

Supply: IESO

The size of the buildout displays each rising demand and structural imbalance. Greater than 1,800 km of transmission growth is already deliberate or underway throughout the province, based on system planning supplies, because it shifts towards large-scale grid enlargement to accommodate electrification.

Stakeholder submissions point out the trail ahead stays contested. Ontario Power Generation recognized potential for as much as 10,000 MW of future era growth at its Wesleyville web site and really helpful inclusion of a number of areas in planning research.

TC Energy supported growth of a 500-kV double-circuit line between the Bruce nuclear complicated on Lake Huron and Essa, north of Toronto, tied to future era and storage tasks, together with its proposed 1,000-MW Ontario Pumped Storage Mission.

Hydrostor urged analysis of bulk-connected non-wires options alongside transmission enlargement, whereas the Energy Employees’ Union raised considerations that higher-end demand development eventualities will not be totally captured in planning assumptions, based on IESO’s suggestions abstract.

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IESO’s procurement framework signifies transmission enlargement will proceed in parallel with new provide acquisition. Medium- and long-term procurement applications are already underway to safe further capability, with planning horizons extending into the 2030s.

The planning file reveals a grid underneath escalating pressure. If superior on the scale reported, this system would rank amongst North America’s largest high-voltage buildouts, making a multiyear building pipeline tied on to Ontario’s electrification trajectory.

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