Ontario’s electricity demand reached 145.6 TWh in 2025 and continues growing at over 4% annually, with projections ranging from 207 to 297 TWh by 2050 depending on economic scenarios. The province faces a significant energy shortfall beginning in 2032, when it will need more than 8 TWh of additional annual electricity generation. By 2035, this gap widens to over 12 TWh, with a summer capacity shortfall emerging only later that year at approximately 950 MW.
Unlike a simple capacity problem, Ontario’s challenge involves matching different electricity generation sources to specific grid needs. Wind and solar farms generate variable output based on weather conditions, batteries store and redistribute power to peak demand hours, hydroelectric resources provide both energy and flexibility, and nuclear plants deliver consistent low-carbon generation. The province has recently resumed procuring renewable energy after more than a decade without major new projects, signing 1,115 MW of wind and solar facilities expected to produce 2.37 TWh annually at costs 21% below previous comparable procurements.
Ontario has simultaneously begun contracting battery storage capacity, with over 3.5 GW under contract by 2030. The latest procurement achieved 36% lower costs than an expedited program and 16% lower than a standard procurement, demonstrating how repeat purchasing can reduce technology costs. These resources address a critical problem: Ontario’s fossil fuel generation increased substantially from 2020 to 2025, with transmission-connected gas generation rising from 9.7 TWh to 31.4 TWh as nuclear facilities underwent refurbishment and experienced outages.
The province’s nuclear refurbishment program has performed well, with both Darlington and Bruce Unit 3 completing ahead of schedule and under budget. However, proposed small modular reactors at Darlington represent greater uncertainty, as Ontario has not built new reactors in decades and the GE Hitachi BWRX-300 design differs significantly from the province’s existing CANDU fleet. Future large-scale nuclear decisions at sites like Wesleyville and Bruce C should be deferred pending better information about long-term demand trajectories and cost trends in renewables and storage technology.
Analysts recommend Ontario pursue flexible generation sources first, continue operating existing nuclear plants when economically justified, learn from the initial SMR construction, and preserve options for larger future nuclear builds. The optimal generation mix depends on which demand scenario materializes and how renewable and storage costs evolve, rather than predetermined commitments to specific technology categories.
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