The scorching summer season of 2025 has led to ranges of electrical energy utilization not seen in additional than a decade in Ontario.
The Impartial Electrical energy System Operator (IESO), which manages Ontario’s energy system, informed World Information that this summer season has been one for the document books.
“Throughout the warmth wave in late June this yr, peak demand reached 24,862 Megawatts (MW), the very best peak since 2013,” Michael Dodsworth, senior advisor of communications with the IESO, mentioned in an Aug. 27 assertion.
“Earlier this month, temperatures once more surpassed 30 C for a number of days, with peak electrical energy demand topping 24,789 MW. The best electrical energy demand from final yr was surpassed eight instances this summer season.”
Throughout a median summer season in Toronto, surpassing 30 C occurs about 17 instances, World Information meteorologist Anthony Farnell mentioned.
This summer season, Toronto topped 30 C 24 instances; that solely occurred 10 instances final yr, and half of these days have been in June, he mentioned.
Moreover, Farnell mentioned Toronto topped 32 C 14 instances this summer season, doubling the annual common. Throughout a warmth wave in June, temperatures hit a nine-year excessive of 36 C and the humidex hit an all-time June excessive of 46, he added.
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“Each additional diploma added to the excessive temperature places an exponentially greater pressure on {the electrical} grid,” Farnell mentioned.
“Additionally, hotter in a single day temperatures imply AC models are working in a single day 24-7 to carry the within temperatures down. The temperature stayed above 20 C for twenty-four nights this summer season, which can be double the typical.”
In June, Farnell forecasted a sizzling summer season for Ontario and Quebec, saying that whereas June could be a transitional month after a cool Could, July and August would carry humidity ranges above regular.
Trying again, Farnell mentioned southern Ontario had six warmth waves this summer season, with temperatures operating one to a few levels above regular for the season.
Did residential hydro price extra?
Warmth apart, Farnell added that smoke and poor air high quality from a number of wildfires meant extra households stored their home windows closed, even when the climate turned cooler outdoors.
For residential Toronto Hydro clients in July, almost 5 per cent extra electrical energy was used in contrast with the identical time final yr, spokesperson Brie Davis mentioned.
“That is largely because of extra frequent and extended use of air-con throughout excessive warmth we now have skilled in 2025,” she mentioned in a press release.
Davis added that this led to a change in client payments.
“A residential electrical energy invoice contains native distribution prices and provincial transmission and technology prices. The native (Toronto Hydro) distribution expenses are set on a set foundation, so they don’t go up or down primarily based on buyer utilization, even when the climate could be very sizzling,” she mentioned.
“The provincial transmission and technology prices do change primarily based on buyer utilization. In comparison with final July, a typical buyer might even see a rise of about $7 in these expenses primarily based on higher electrical energy consumption because of excessive warmth.”
Hydro One, the province’s largest electrical energy utility, noticed roughly a 3 per cent soar in residential electrical energy utilization between Could and July compared with that very same time in 2024, spokesperson Bianca Pizzo mentioned. That translated to a median improve of $3 to $4 a month, she added.
Each Hydro One and Toronto Hydro mentioned they’ve a number of applications accessible for purchasers trying to assist save on vitality prices.
Regardless of the elevated utilization this summer season, Dodsworth mentioned Ontario’s energy community has held up properly.
“Even with this excessive demand, the IESO management room has been capable of leverage Ontario’s various provide combine that features wind, photo voltaic, hydro, pure fuel, nuclear, and vitality storage to maintain the lights on,” he mentioned.
“These totally different assets have totally different traits and responses to climate, that means we all the time have assets to attract on which can be proper for the second.”
As for the remainder of the summer season, which formally ends Sept. 22, Farnell mentioned extra chilly days are in retailer for southern Ontario.
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