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Keeping Phoenix livable in summer is creating record demand for electricity

What if a prolonged power outage knocked out air conditioning for everyone in Phoenix during a heat wave? A  study in the journal Environmental Science and Technology published in May considered that worst-case scenario. Researchers found nearly half the city’s population — about 800,000 people — would need emergency care. Nearly 13,000 would die.

“In hot cities, air conditioning is a critical lifeline in the summer,” said David Hondula, director of Phoenix’s Office of Heat Response and Mitigation and one of the study’s co-authors.

Hondula emphasized he does not expect this scenario will actually happen.

“We’re talking about slivers of a fraction of a percent of possibility,” Hondula said.

But, he said, the findings do underscore just how important it is to keep Phoenix’s power on.

And that is becoming more of a challenge for providers each year.

Phoenix is currently in the longest stretch of days ever recorded with high temperatures of at least 110 degrees. This brutal heat wave is leading to record electricity usage, with both of Phoenix’s electric providers — Arizona Public Service and Salt River Project —  reporting their highest demand ever in the last week.

“We’re one of the fastest-growing areas of the U.S., so it’s not too surprising to see our peak demand needs increasing year over year,” said Pam Syrjala, SRP’s director of supply, trading and fuels.

And as metro Phoenix's population grows, climate change is making the region's summers hotter and its heat waves longer. That’s also contributing to the increasing strain on the region’s utilities.

“Air conditioning is probably one of our single largest loads,” Syrjala said.

Syrjala said the huge demand of hot summer afternoons is what SRP plans for all year. The strategy is to be able to draw from a variety of power sources — coal, natural gas, nuclear power and renewables.

“No one resource really solves the whole energy need. So you have to make sure that you have the right mix of resources in your portfolio to ensure reliability,” Syrjala said.

And Syrjala said SRP continues to look for ways to add backup power to that mix.

In anticipation of growing demand, SRP in fall 2022 installed two new 49.5-megawatt natural gas turbines at its Agua Fria Generating Station in Glendale. When demand on SRP’s grid is peaking, the new units can start generating enough power for 22,000 homes in under 10 minutes.

“They are fast. Very, very responsive,” said plant director Bob Ellis.

Older peaking turbines at the Agua Fria plant have been there since the late 1950s and, while they still work, Ellis said they take 12 to 14 hours to get turned on.

“You’ve got a big hunk of steel, that steam turbine, and you have to warm that up to make sure it’s evenly warmed before you actually put it online,” Ellis said.

SRP is good at predicting when hot weather is coming and when additional power will be needed. But the utility can’t always plan 12 to 14 hours ahead.

Ellis said the new, faster, peaking turbines mean SRP is better prepared for disruptions than ever before.

“We get a lot of fluctuations,” Ellis said. “Maybe another power plant tripped, it could be a monsoon that came in and wiped out a bunch of transmission lines, it could be a cloud going over a solar field, but we use these to smooth out the grid.”

The Agua Fria Generating Station is also home to one of SRP’s newest battery storage sites, where Tesla Megapack batteries installed in 2021 hold enough backup energy to keep about 5,000 homes powered for four hours. SRP expects to have about 40 times that battery capacity available system-wide by 2024.

The Valley’s other provider, APS, said it relies on a similar mix of power sources to prepare for peaks.

And both utilities also offer incentive programs to encourage customers to conserve during times of high demand. APS spokesperson Yessica Del Rincon said even small changes like switching to LED lightbulbs can help.

“Actually those LED lights emit less heat, which means that your house can stay cooler,” Del Rincon said.

SRP and APS say storms are the most likely cause of summer outages. And part of the reason it has been so hot this July is because there has been so little monsoon activity this season.

But, according to Hondula’s study, extreme weather and natural disasters nationwide are making blackouts much more common than they used to be. Outages impacting more than 50,000 customers for more than an hour have become more than  twice as frequent since 2015.

While chances of a major blackout in Phoenix are still slim, Hondula said the study serves as a reminder that if disaster strikes, a cooler city would be a safer one. His office is advocating for Phoenix to plant more shade trees and increase the use of cool roof technology. 

“The attention the study received actually provided a lot of validation for some of the programs we’ve been trying to stand up, and some of the funding we’ve been pursuing,” Hondula said.

As Phoenix’s population keeps growing and temperatures keep climbing, he said the city will have to continue to look for heat relief strategies beyond just air conditioners.

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Katherine Davis-Young is a senior field correspondent reporting on a variety of issues, including public health and climate change.