1. The Documented Gap

Ontario's Independent Electricity System Operator publishes an Annual Planning Outlook that forecasts demand, assesses reliability, and identifies where supply falls short. The 2026 edition, released in March, projects incremental energy needs of 8.5 terawatt-hours emerging by 2032 in the reference scenario. [1] By 2035, the capacity shortfall rises to 950 megawatts. By 2040, it reaches 3,800 MW and 37 TWh. [1]

The near-term picture is marginally better than it was a year ago. IESO notes the improvement reflects resources recontracted through its second Medium-Term RFP and slightly lower demand in the reference scenario. [1] The 2025 APO had put the equivalent capacity gap at 2,100 MW by 2034. That figure has come down. But the direction has not changed: demand is growing faster than committed supply can follow, and the gap widens with every year of the outlook.

The demand side keeps getting revised upward. IESO's 2025 APO forecast a 75% increase in net annual energy demand by 2050, reaching 262 TWh, up from the 60% projected just one year earlier. [2] The 2026 APO moderated this to 65% growth, reaching 250 TWh, reflecting a lower EV adoption forecast and economic headwinds from trade disruptions. [1] Ontario's own Integrated Energy Plan, released three months after the 2025 APO, discusses higher-growth cases of up to 90%. [14] The public numbers vary by document and scenario, but all point the same direction. The spread matters because supply planning is highly sensitive to demand assumptions, and the supply gap widens under every version.

The drivers are the same ones identified in Part 1 of this series: electric vehicles, heat pumps, data centres, industrial electrification. EV-related demand alone accounts for 20 TWh of new load by 2035, with industrial growth, including EV battery plants, steel electrification, and hydrogen production, adding another 23 TWh. [3] Data centres represent a separate and fast-moving pressure. At a Toronto Region Board of Trade panel in late 2025, IESO Chief Energy Transition Officer Chuck Farmer disclosed that the connection queue included 8,400 megawatts of data centre demand, roughly one-third the size of Ontario's entire electricity system. [19]

On June 4, 2026, the federal government released its AI strategy, which states that partnerships are being finalized to provide 850 MW of sovereign AI computing capacity by 2030. [22] That target represents additional federal demand on top of the 8,400 MW already in IESO's connection queue. The federal government is actively soliciting new electricity demand while the grid planner says gas is required for reliability through the late 2030s.


2. The Nuclear Bet

Ontario's plan to close the gap depends overwhelmingly on nuclear power. The Integrated Energy Plan envisions nuclear supplying more than 70% of Ontario's electricity by 2050, requiring up to 17,800 MW of new nuclear capacity on top of the existing fleet. [14] The plan begins with a single reactor.

The Darlington BWRX-300, developed by GE Vernova Hitachi Nuclear Energy, is a 300-megawatt small modular reactor under construction at the Darlington site on the north shore of Lake Ontario. The Canadian Nuclear Safety Commission issued a Licence to Construct on April 4, 2025. [11] The reactor building foundation was set on May 1, 2026. The target is commercial operation by the end of 2030. [10]

The original public framing was conditional. When OPG and GE Hitachi announced the project in December 2021, the reactor was described as one that "could be completed as early as 2028." [9] The current commitment is end of 2030. The public target moved from a conditional early framing to a firm date, and the firm date is later.

Even if Unit 1 delivers on time, the arithmetic is clear. A 300 MW reactor operating at a 90% capacity factor produces roughly 2.36 TWh per year. IESO's 2032 energy gap, in the reference scenario, is 8.5 TWh. Unit 1 covers approximately 28% of it. Three follow-on units are planned for the 2033 to 2036 window, which would bring the Darlington SMR fleet to roughly 1,200 MW and 9.4 TWh. Beyond that, the next tranche of nuclear, including a potential Bruce C expansion of up to 4,800 MW, has no committed in-service date. A pre-development agreement was announced in May 2026. Earliest commissioning on standard new-build timelines would be late 2030s at best. [14]

The construction timeline is where the documented record runs hardest against the schedule. The World Nuclear Industry Status Report found that the average construction time for the 18 reactors connected to grids globally between 2021 and 2023 was approximately 10 years. [12] The World Nuclear Association's own data corroborates the underlying grid-connection figures, confirming seven reactors were connected in 2024 across China, France, India, the UAE, and the United States. [21] WNISR's 2025 edition reported that fewer than a third of expected grid connections materialized that year, with four reactors connected against a beginning-of-year expectation list of 13. [13] Western projects fare worse. Vogtle Units 3 and 4, the only reactors completed in the United States in over three decades, each took more than a decade and cost more than double their original estimates. Flamanville-3 in France took 17 years.

No BWRX-300 has been completed anywhere in the world. There is no reference plant for any regulator, builder, or investor to point to. The Darlington project is not just Ontario's first new reactor in a generation. It is the first of its kind globally. [13]

OPG's record on its most recent nuclear project, the Darlington refurbishment, is more encouraging. The company reported the four-unit refurbishment came in approximately $150 million below the $12.8 billion budget and four months early. [15] The Ontario Auditor General's 2018 report found that 18 prerequisite projects ran more than $725 million above their initial estimates, though about $345 million of that overrun had been incorporated into the $12.8 billion project estimate. [16] Separate OPG filings identify additional turbine and generator lifecycle work outside the 2016 refurbishment scope. Those costs do not mean the refurbishment was over budget, but they complicate the headline framing. [15] None of this makes OPG unusual among nuclear operators. It does make the C$20.9 billion SMR fleet estimate, announced by the Minister of Energy and Mines in May 2025 without an Ontario Energy Board review comparable to the refurbishment disclosure, worth independent scrutiny. [10]


3. What Actually Fills the Gap

The gap exists now. The nuclear supply arrives later, if it arrives on schedule. Something has to generate the electricity in the interim. The documented record shows what that something is.

IESO's Long-Term 1 procurement, completed in May 2024, secured approximately 411 MW of non-storage capacity, almost all of it natural gas, alongside 1,784 MW of new battery storage. [6] The largest gas award was the 405 MW Napanee Generating Station expansion, a simple-cycle gas turbine. Under the LT1 contract terms, the expiry date for natural-gas facilities is April 30, 2040, meaning the Napanee expansion is contracted to operate through the end of that decade. [7] Earlier IESO expedited and same-technology procurements secured additional gas capacity beyond the LT1 totals. The battery storage provides peak shifting, not net new energy. Gas provides both.

Three months after the LT1 results, Ontario Energy Minister Stephen Lecce directed IESO to change its second long-term procurement from "non-emitting" to "technology agnostic," explicitly opening the door to additional gas. [8] The directive was issued on August 28, 2024. The rationale was reliability. The effect is that Ontario is contracting for gas-fired generation through 2040 under LT1, and is open to additional gas under LT2 that could extend further.

This is not a contingency plan. It is the plan. IESO's 2025 APO Capacity Expansion Scenario states that gas generation "is modelled to operate at levels far below its capability and can provide more energy as necessary." [5] The 2025 APO summary puts it plainly: gas generation will be required for reliability into the late 2030s and beyond. [20] The system has spare gas capacity. If nuclear is late, gas runs harder.

The measured outcome is already visible. Ontario's grid carbon intensity rose 25% in 2024, reaching 73.8 g CO₂eq/kWh. The Toronto Atmospheric Fund attributed the increase to "the province's increasing reliance on gas-fired electricity generation." [4] It is worth noting that reduced nuclear availability during the Darlington refurbishment contributed to higher gas dispatch in 2024. Whether the increase represents a durable trend depends partly on nuclear refurbishment recovery and future gas dispatch patterns. But the direction in 2024 was unambiguous: the grid got dirtier in the year the electrification strategy was supposed to begin delivering cleaner power.


4. The Carbon Price on the Bridge

On April 1, 2025, the consumer fuel charge was set to zero. The price Canadians paid on gasoline, home heating fuel, and natural gas disappeared from their bills. But the federal Output-Based Pricing System, which applies to large industrial emitters including gas-fired electricity generators, remained in effect. [17]

The OBPS works through a declining output-based standard. For new gaseous electricity generation, the standard started at 206 tonnes per gigawatt-hour in 2025 and falls to zero by 2030. [17] Once the standard reaches zero, covered generators pay the industrial carbon price on all emissions, not just the excess above a benchmark. At $170 per tonne in 2030, a combined-cycle gas plant emitting roughly 0.37 to 0.45 tonnes per MWh would face an additional cost of approximately $63 to $77 per megawatt-hour. A simple-cycle plant, like the Napanee expansion, could face $94 to $111 per MWh. [17]

That cost is not a line item on a consumer's hydro bill, but it is embedded in the electricity rate. Every heat pump that replaces a gas furnace, every EV that replaces a gasoline car, shifts household energy consumption onto the electricity grid. The switch can still reduce household emissions, particularly for heat pumps, which use electricity roughly three times more efficiently than a gas furnace produces heat. The cleaner the grid, the larger the benefit. But Ontario's planning documents show the marginal generation source is gas through the late 2030s, and the industrial carbon price applies to that generation.

The federal National Electricity Strategy, released in May 2026, frames the grid build-out as essential to "affordability, economic growth, and climate change." [18] It commits to doubling Canada's electricity supply by 2050. It does not reconcile this commitment with the grid planner's documented reliance on gas-fired generation for the next two decades. The electrification plan is real. The demand it creates is real. The clean supply it assumes is not here yet, and the documents that tell us what fills the gap in the interim are the government's own.