TORONTO — The Ontario government’s approval of a new underwater electricity transmission line into Toronto comes weeks after the province signed a cross-border nuclear cooperation agreement with New York State, and months after Premier Doug Ford publicly threatened to cut off electricity exports to the United States during a trade dispute.Earlier this winter, Ford and New York Governor Kathy Hochul signed an agreement committing both jurisdictions to work together on expanding nuclear power, including large-scale reactors and small modular reactors. The deal includes a memorandum of understanding between Ontario Power Generation and the New York Power Authority and references the potential expansion of electricity trade between the two grids..The new transmission approval follows that agreement and highlights Ontario’s effort to expand both electricity generation and domestic transmission capacity as demand rises and geopolitical tensions over energy exports persist.In March 2025, Ford warned that Ontario could cut electricity exports to U.S. states if trade actions harmed the province.“If they want to try to annihilate Ontario, I will do anything, including cutting off their energy — with a smile on my face,” Ford said at the time, following his third majority election victory.“They need to feel the pain. They want to come at us hard? We’ve got to go back twice as hard.”.Ontario is a major electricity exporter to New York, Michigan and Minnesota, with seven cross-border interties providing a combined transfer capacity of roughly 2,500 megawatts.Between 2021 and 2023, Ontario exported more than 40 terawatt-hours of electricity to U.S. states, accounting for about 9% of total provincial generation during those years.Against that backdrop, Ontario has now approved a recommendation from the Independent Electricity System Operator to build a third major transmission line into Toronto.The project would deliver electricity via a high-voltage underwater cable from near the Darlington nuclear site to the city’s downtown and eastern core..The proposed line would add up to 900 megawatts of capacity to Toronto’s electricity system. Provincial planners say the city’s existing transmission corridors — one from the west and one from the east — are expected to approach capacity in the 2030s as population growth, housing construction, transit electrification and electric vehicle adoption increase.Energy and Mines Minister Stephen Lecce said the additional transmission infrastructure is needed to prevent electricity constraints from limiting economic development and housing construction in Ontario’s largest city.According to the IESO, Toronto’s peak electricity demand currently sits at approximately 4,700 megawatts, representing about 20% of Ontario’s total peak demand. Forecasts suggest that demand could nearly double by 2050.The underwater route was selected following technical analysis that found it would deliver more capacity than alternative options while minimizing land-use impacts and reducing vulnerability to extreme weather events. The IESO estimates the project could avoid between $100 million and $300 million in future bulk system upgrades elsewhere in the Greater Toronto Area..The province has directed the IESO to pursue a competitive procurement process to select a transmission developer, with consultations planned on procurement design and Indigenous participation. Construction and commissioning are expected to take between seven and 10 years.The transmission project is outlined in the 2025 Toronto Integrated Regional Resource Plan and aligns with Ontario’s broader nuclear expansion, including refurbishment work at Darlington and plans to build four small modular reactors at the site.While the new transmission line is intended to serve domestic demand, its approval comes amid heightened attention to Ontario’s role as both a power exporter and a nuclear technology partner to U.S. jurisdictions. Together, the nuclear agreement with New York and the Toronto transmission expansion underscore the province’s efforts to strengthen its electricity system at a time when energy security has become increasingly politicized.
