Scorching summers test Ontario’s electricity grid; nuclear gets a boost while green energy lags behind
Joel Wittnebel/The Pointer

Scorching summers test Ontario’s electricity grid; nuclear gets a boost while green energy lags behind

On August 14, 2003, the lights literally went out and darkness fell upon much of Ontario and the northeastern United States due to a blackout that left over 50 million people without power. 

The sweltering heat had pushed grids across the eastern seaboard beyond their limit. Residents across the GTA took to the streets. Restaurants and bars offered free drinks and food instead of letting their supplies waste away. The black of night was lit by thousands of candles in what many celebrated as a return to the simpler life.

Others warned it was a sign of a trend that could soon speed up. 

It has been classified as the largest electricity outage in North American history.

One of the causes was the degraded condition of the power infrastructure in the state of Ohio, which sent surges of electricity between 2,000 and 4,000 megawatts into Ontario’s grid connections at Michigan and New York. The overload was more than the web of electricity infrastructure could handle, and large parts of Ontario and the northeastern U.S. were blanketed in darkness when the cascading surges shut down every light grid by grid. It took nine days of restoration efforts before the emergency ended.

The peak Ontario electricity demand that day, just before the blackout hit, was 24,072 megawatts. Today, Wednesday, July 5, the peak market demand in Ontario was projected to reach 23,962 megawatts at 7 p.m., as temperatures across the GTA remained in the low 30s not factoring humidity, even as the sun began to set. The all-time peak record is 27,005 megawatts used on August 1, 2006.

“The province's electricity system has changed considerably since the blackout,” the Independent Energy Systems Operator (IESO) wrote in a blog post years after the mass power outage. “Today, with more generators, more demand response, more local generation and increased interconnections, we have a larger supply cushion and new tools and procedures to help ensure the efficiency and reliability of the grid.”


Demand for electricity peaked in Ontario on August 14, 2003 at approximately 3:45 pm before the grid surged and a blackout ensued across most of the province and the eastern seaboard.

(Independent Electricity Systems Operator)


Even though the grid is more resilient than it was in 2003, one concern that has been raised is if the grid can handle increased pressure from heat waves that are predicted to sweep across the province as our summers begin to swelter at unprecedented temperatures. 

“There's demand on the grid [from air conditioner usage]. And then at the same time, extreme heat is a time where the electricity grid is actually less efficient, in terms of the engineering system,” Joanna Eyquem, managing director of climate-resilient infrastructure at the Intact Centre on Climate Adaptation at the University of Waterloo, said.

In June, Environment and Climate Change Canada (ECCC) released its summer outlook for 2023 concluding that July and August would be characterized by higher than normal temperatures scorching much of the province. Average summer temperatures for southern Ontario are in the mid 20s — with humidex values added on top — but the outlook from ECCC warns that the number of extreme heat days, where temperatures tip well above average, is rising. 

Today, in the midst of an almost week-long extreme temperature warning, the temperature including humidity reached 40 degrees across much of Southern Ontario. U.S. scientists declared, according to global data, that Monday, July 3, was the hottest day ever recorded on the planet.

In Toronto and Hamilton on April 13 the temperature reached 28 degrees — almost ten degrees above the average and the hottest day for that date ever recorded. While May brought temperatures back down to the ‘normal’ or historical average range, June also started off scolding with a heat warning issued for much of the province.

Wildfires have spread across parts of Canada and the U.S. since the spring in the worst season for forest blazes this country has ever seen, and we’re only two weeks into  the summer. 

The global average temperature on July 3 reached 17.01 degrees, according to the University of Maine’s Climate Reanalyzer, the first time the average planetary surface temperature has surpassed 17 degrees in the dataset’s 44-year history.

“Global warming, as it suggests, means that we're going to see an increase in annual temperatures,” Eyquem said. “But on top of that we have the increased frequency of extreme heat events.”

Eyquem told The Pointer that some areas could see the number of hot days — when the temperature reaches 30 degrees or above — multiplied three or four times by 2050. With the mounting pressure heat puts on the electricity grid, topped by the continual need to run air conditioners, along with other electricity demands such as increased refrigeration, it could overwhelm existing capacity that our electricity grid is designed for. Failure of the system could leave many people at risk. 

“If an extreme heat event coincided with an extended power outage — with no electricity supply to air conditioners and fans — lack of preparedness could result in widespread fatalities,” Eyquem wrote in a report for the Intact Centre. 


A super surge within the electricity system, which could result from a scorching heat event, would turn brightly lit bustling cities into darkness.

(Independent Electricity System Operator)


According to the IESO, on a day like Wednesday, where temperatures across most of southern Ontario topped 30 degrees, peak demand could surpass 23,000 megawatts, while 24,283 are available to be supplied. 

Some authorities are beginning to open their eyes to the threat the heat poses to the population, but there is still a disconnect. Research shows that even if greenhouse gas emissions completely stopped today, there would still be a 42 percent chance that Earth would surpass the 1.5 degrees of warming that represents a dangerous tipping point. The globe would continue to heat up for approximately 40 more years from residual emissions before temperatures levelled out and potentially began to decrease. 

The PC government has responded to the need to meet rising demand for electricity by turning to natural gas. In October, the Ontario government announced the investment of an additional 1,500 megawatts of electricity from natural-gas (on top of the 10,000 that can currently be produced by gas plants). The announcement came just a week before the World Meteorological Organization (WMO) warned that the supply of electricity from clean sources must be doubled by 2030 to limit global temperature increase.

But even prior to the October announcement, Ontario’s electricity grid was headed backwards. A report from The Atmospheric Fund (TAF) showed that emissions from the electricity grid rose 28 percent in 2021 citing an “increasing use of natural gas-powered generating plants, which increase the carbon intensity of the Ontario electricity grid overall.”

Increasing the burning of fossil fuels will only add to the snowball effect, increasing temperatures and driving up demand for electricity to keep people cool. On Wednesday, the Ontario government announced pre-development work for new nuclear generation at Bruce Power. While nuclear is a zero carbon source of electricity, it has its skeptics due to the potential for a nuclear accident and concerns around how the waste can be safely stored. Meanwhile, the PC government has done very little to invest in renewable energy technologies and in its first term, cancelled 750 contracts for renewables signed by the previous Liberal government.

According to the Independent Electricity System Operator, which administers Ontario’s market, 34 percent of the province’s electricity supply comes from nuclear; 27 percent from gas; 23 percent from hydro; 13 percent from wind; 1 percent from solar; and less than a percent from biofuels. The lack of progress in the green energy sector runs counter to many jurisdictions around the world where wind and solar energy investments have exploded. Sweden, for example, reached its goal of supplying 50 percent of its electricity from renewable sources in 2012 and is on track to reach 100 percent by 2040.

The air quality index for much of Ontario was in the high risk category in late june as wildfires raged across parts of Quebec. The conditions are expected to continue throughout parts of the summer.

(Joel Wittnebel/The Pointer)


Eyquem said it is important for municipalities to take on community adaptation as the stifling heat becomes inevitable. Planting trees to create cooling canopies, information around the use of blinds and efficient air conditioning are just some of the things residents can be educated on. 

“I don't think people necessarily have been thinking about this as potentially such a serious health issue,” she said. “I think people may be thinking, ‘Oh, that's maybe going to be a bit more uncomfortable for a few days of the year. But I'm just going to turn my AC on’.”

Provincial and municipal policies lack the detail to protect people facing extreme heat. The provincial  Building Code, for example, does not classify extreme heat as an emergency situation so emergency policies for backup power during a power outage are far less stringent than those in place for a hurricane. For Eyquem, this is unacceptable, especially when you are dealing with vulnerable populations.

“Particularly where vulnerable people are, like hospitals and senior care homes, having backup power is an important consideration.” 

A spokesperson for the City of Mississauga told The Pointer in an email that the City is prepared to deal with hotter than average temperatures and will be continuously monitoring weather forecasts throughout the summer. The City opens up swimming pools, air-conditioned libraries, spray pads and air-conditioned community centres for people to visit during extreme heat days and extends hours of operation for splash pads and community pools. In addition, the City has a temperature bylaw which dictates that during the summer months, landlords cannot allow indoor temperatures to exceed 26 degrees. 

But while Mississauga has enacted such bylaws, the PC government is once again moving backward, categorizing air conditioning as a luxury that can cause rent to be increased. Under the proposed Bill 97, the province’s newest set of policy changes to help achieve the goal of 1.5 million new homes across the province by 2031, landlords will be allowed to increase rent in units that have air conditioning, and this will not be subject to the 2.5 percent cap on annual increases. 

“Tenants’ apartments are getting hotter because of the climate crisis and can lead to extreme health issues,” wrote ACORN Canada, a tenants rights group. “Deaths due to extreme heat are on the rise so having air conditioning is no longer about comfort, it’s about health.”

While the City of Mississauga has some measures in place to deal with extreme temperatures — along with the Region of Peel which operates designated cooling centres — Eyquem said municipalities still have a long way to go in dealing with heat events that are becoming more common. 

“I think cities that have experience like Montreal in 2018, Vancouver and surrounding areas in 2021, are each making progress to learn how to deal with this better,” she said.

The heat experienced so far this summer will not be a one off, in fact it may be one of the coolest summers to come. The world is entering an El Niño period which is typically associated with warmer than average temperatures. 


2016 was one of the strongest El Niño events on record; the red represents warmer than normal ocean temperatures and the blue represents cooler than normal ocean temperatures.

(National Oceanic and Atmospheric Administration)


During El Niño, easterly winds cause warm water to be pushed back east toward the west coast of the Americas. The warmer waters cause the Pacific jet stream (the air above) to shift farther south leaving parts of Canada and the northern United States warmer and drier than normal. 

El Niño is often followed by La Niña which has the opposite effect. Trade winds blow with more force pushing warm water toward Asia while cold air moves north west of North America. This cools the jet stream as it shifts to the north causing cooler, wetter weather across much of Canada. 

But we cannot wait for La Niña for relief. In May, the WMO predicted with 98 percent certainty that at least one of the next five years, as well as the whole five year period, will be the hottest on record. It also stated there is a two in three chance that El Niño will help push the planet above the 1.5 degree warming threshold between 2023 and 2027. Once this target is hit, even if only temporarily, it will be hard to turn back. At that point, the world has to shift into an adaptation mode, as mitigation would do little to reverse course by then.

Eyquem said increased heat needs to be contemplated by all residents who should start thinking about how to adapt.

“I don't think the need for people to think about their own adaptation has generally got through either," she said. “In conversations I'm having with my neighbours, most people, when hearing the word climate or climate action, immediately started talking to me about emissions reduction or carbon. And on the side of adaptation, relatively little attention has been paid to it.”

She stressed that some adaptation measures can help mitigate the impacts of climate change, and overall contribute to a higher quality of life in a “win-win” situation. She used the example of a green alleyway which can help with adaptation by providing cooler shade cover, while also planting trees to help with carbon sequestration. Simultaneously, it provides a place for people to be outside which impacts both physical and mental well being.

“Anytime we're improving people's access to nature and natural areas is obviously better for mental health and well being and quality of life. So the message is adaptation is, yes, it's reducing risk, but it's also making life safer and better.”


Email: [email protected]

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