Why a power outage amid this Phoenix heat wave would be so deadly

July 2024 · 5 minute read

As the heat wave scorching millions of people across the Southwest intensifies, the upcoming days will be a test for Phoenix.

Temperatures are forecast to soar to among the worst in history and set records for electricity demand. Experts worry that this combination could create a nightmare scenario: a brutal heat wave and multiday blackout that, according to one study, could kill thousands of people and send half the city to the emergency room.

“A blackout during a heat wave is probably the most threatening climate event we can imagine,” said Brian Stone Jr., the lead author of the study and a professor at the Georgia Institute of Technology’s School of City and Regional Planning.

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To be clear, the likelihood of such a scenario — especially one as dire as the paper foreshadows — is low in a city such as Phoenix, where city officials and electricity providers say the power grid is highly reliable. However, the risk is heightened during severe heat waves, which hike regional demand for power and compromise the functioning of energy infrastructure.

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The threat is not limited to Phoenix: Two-thirds of North America is at risk of energy shortfalls this summer, particularly during periods of extreme demand, according to a report from the North American Electric Reliability Corporation.

Meanwhile, 108 million Americans are under heat alerts as unforgiving temperatures bake much of the Lower 48. In addition to the Southwest, where temperatures could climb as high as 130 degrees, the nation’s three most populous states — California, Texas and Florida — are facing triple-digit temperatures. The magnitude and duration of the heat is setting records.

“We can call [the scenario identified in the paper] overly dramatic, but we’re breaking local and global heat records every day now it seems, so we have to take it seriously,” said Michael Webber, a professor and energy expert at the University of Texas at Austin. In Phoenix, he said, the grid is “robust,” but the stakes for failure are high.

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The study’s researchers simulated what would happen if the residents of Phoenix, Atlanta and Detroit were struck by a heat wave and a complete blackout that lasts 48 hours before power starts to be incrementally restored. The outcomes were deadly in all three cities, but the results for Phoenix were particularly striking, where almost everyone in the city relies on air conditioning to weather extreme heat. The study predicted that about half the population would require emergency department care and about 13,000 would die.

“Phoenix has a resilient electrical grid, there’s no doubt about it,” Stone said. “But they really haven’t prepared sufficiently for that low-probability but very high-impact event.”

Stone warned that climate change increases the likelihood of the nightmare scenario the paper examined. Heat waves are anticipated to become more intense, frequent and prolonged. Meanwhile, power grids will face increased demand for electricity during the summer months while being stressed by extreme weather, such as heat waves, hurricanes and wildfires.

Scientists say to brace for more extreme weather and possibly a record-warm 2023 amid unprecedented temperatures. (Video: John Farrell/The Washington Post)

Since 2015, the number of major blackouts — power outages lasting more than an hour and impacting more than 50,000 customers — have more than doubled, according to the study. Electric grid failures likely contributed to hundreds of deaths and thousands of emergency department visits during the historic 2021 Pacific Northwest heat wave, the study said.

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Ashley Ward, the director of the Heat Policy Innovation Hub at Duke University, said the study is “valuable” and captures the magnitude of the impact of heat. She noted that the study does not take into account humidity when estimating health outcomes, which she said could worsen the number of ER visits and deaths in Gulf Coast and Southeastern cities.

“It’s really troubling,” she said of the study’s findings in light of the current heat dome smothering the Southwest. “I think the truth is our energy grid is just not necessarily up to the task of the demands of such extreme daytime temperatures.”

Zachary Schlader, an associate professor at Indiana University Bloomington who has studied the effect of thermal stress on the human body, added that research into worst-case scenarios can help public health officials avert bad outcomes, even if a heat wave and blackout are unlikely to coincide.

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On the ground in Phoenix, officials and grid operators are preparing for temperatures that are forecast to reach highs of 118 degrees over the weekend.

In a statement, Mayor Kate Gallego said the scenario presented in the study is “extremely unlikely” to occur and did not take into account existing emergency management resources. “We are lucky to have a very reliable electric grid in Arizona and city personnel who work day in and day out to ensure we’re prepared for complex emergencies,” she said.

The Salt River Project and Arizona Public Service, the two main electricity providers in Phoenix, also said they are ready to handle the extreme heat, using a mix of energy from hydropower facilities, natural gas plants, nuclear reactors, wind farms and other sources.

The Salt River Project is forecasting demand that could exceed the record set last year, but the utility is confident it has enough capacity to meet that demand, said Pam Syrjala, the director of supply, trading and fuels.

Stone, the lead author, called on every city to start preparing for these kinds of events, such as by investing in street trees and cool roofs designed to reflect more sunlight than a conventional roof — strategies that can offer a reprieve from heat even if the power is out.

“It’s not just Phoenix,” he said. “It’s all cities.”

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