Ontario opens November capacity auction

Ontario's electricity grid operator, IESO, is running its regular short-term capacity auction, where batteries, power plants, imported electricity, and demand-response programs compete to provide backup power availability for a six-month stretch. Resource owners had until September 25 to sign up, with bidding set for November 25-26. The winners will cover a summer 2027 period (May through October) and a winter 2027-28 period (November through April).

This is routine market housekeeping rather than a new program, and it doesn't involve homeowners directly signing up for anything. But it does shape how much backup capacity Ontario has on hand and what it costs. Last year's version of this same auction secured 1,833 megawatts for summer 2026 and 1,125 megawatts for the following winter, at a cost IESO says works out to about 1% of total system costs — a small piece of what keeps the lights on and prices stable.

This short-term auction runs separately from Ontario's longer-term battery storage contracts, which are adding more permanent capacity to the grid. Those deals have already secured 1,784 megawatts of battery storage across 10 sites, plus another roughly 882 megawatts from a faster-moving contracting round, and a further 640 megawatts from three battery projects announced in June. Together, these efforts point to Ontario leaning more heavily on large batteries to balance supply and demand, which over time can help keep the electricity grid more reliable for homes across the province.