Does Ontario have enough electricity? The supply gap, explained
Ontario's grid operator expects new energy needs by 2032 and a 3,800 MW capacity gap by 2040. Here's why, and what's being built.
Ontario's electricity demand is climbing while some of its largest power plants are offline for rebuilds and older supply contracts expire. The province's grid operator, the IESO, now plans for a growing gap between the power we'll need and the power we have.
What the grid operator is forecasting
The IESO's 2026 Annual Planning Outlook forecasts electricity demand growing 65% by 2050 in its reference case, and by as much as 92% in a high-demand scenario driven by economic growth, data centres and faster electric vehicle adoption.1
| Year | New energy needed | New capacity needed |
|---|---|---|
| 2032 | 8.5 TWh | — |
| 2035 | — | 950 MW |
| 2040 | 37 TWh | 3,800 MW |
Those figures are needs beyond the resources Ontario already has or has contracted, driven by rising demand and resources reaching the end of their contracts.1
This isn't a new warning
In 2019 the IESO was already noting that "a capacity need will arise in 2020" that could grow in 2023 as long-term contracts expired and nuclear reactors went offline. At the time, Ontario Power Generation was buying four natural gas plants with nearly 2,700 MW of capacity, partly to prepare for the planned shutdown of the Pickering nuclear station, which supplied about 14% of Ontario's electricity needs.2
Why the gap is opening
- Nuclear rebuilds. Pickering's older units retired in 2024 and its four remaining units came offline in September 2026 for a refurbishment expected to run into the mid-2030s.34 Bruce Power is rebuilding six reactors through the 2030s.5
- More gas in the meantime. Nuclear supplied 61% of Ontario's transmission-connected output in 2018 and gas just 6%.2 By 2025 nuclear was 48.5% of the supply mix and natural gas, oil and other sources 16.6%.6
- Electrification. Heat pumps, electric vehicles, industry and data centres all add demand at the same time.1
How Ontario plans to close it
- Efficiency first. The 2025-2027 demand-side management framework targets 900 MW of peak demand savings and 4.6 TWh of energy savings.1
- New supply. Long-term procurements target up to 1,000 MW of capacity and 11 TWh of energy for 2032-2034, alongside new nuclear at Darlington and possibly Wesleyville.178
What it means at home: every kilowatt a home doesn't waste, and every kilowatt-hour it makes with solar or shifts to overnight with a battery, is demand the grid doesn't have to build for. That's why we start every plan with efficiency.
Sources
Figures are as reported by the sources listed, at the dates shown. Older figures are included for historical context. Canadian Energy Standard is an independent company, not affiliated with any government, utility, generator or energy retailer named here.
- IESO, 2026 Annual Planning Outlook: Ontario's electricity system needs, 2027-2050 (March 2026)
- Financial Post, OPG's gas-plant purchases partly prompted by shifting nuclear landscape (August 2019)
- Ontario Power Generation, Pickering Nuclear Generating Station
- insauga, $26.8 billion nuclear refurbishment to begin in Pickering early next year (August 2026)
- Bruce Power, Life-Extension Program and Major Component Replacement
- Ontario Energy Board, Ontario's system-wide electricity supply mix: 2025 data
- Ontario Power Generation, Darlington small modular reactors
- Ontario Power Generation, Wesleyville new generation opportunity
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