The electric grid faces a looming challenge: longer and stronger heat waves.
Large swaths of California, Arizona, Nevada and Texas are expected to endure more than four months each year in which the temperature will be high enough to threaten power transformers. New research is emerging. As a result, power outages caused by overheating electrical equipment could become more frequent by mid-century.


Days with heat waves that put pressure on transformers
What’s at stake?
Transformers are crucial.
Transformers “slow down” high-voltage electricity so it can flow safely to your home appliances. Without it, electricity cannot be sent over long distances, and the grid will not function. You either live near a power plant or you live without electricity.
They are vulnerable to heat waves.
Like all electrical equipment, transformers perform worse in heat. This could force the power company to implement a blackout. If the temperature remains high for several days in a row, inverters may fail completely, causing power outages.
Power outages during heat waves are deadly.
Air conditioners are more than just pleasant amenities – they are often the difference between life and death. If the power goes out and people are unable to cool themselves, they may suffer heat stroke, dehydration and heart attacks. The elderly and sick are particularly at risk.
New research by consultancy ICF’s Climate Center predicts how temperature will change by mid-century under a moderate warming scenario. They then calculated the number of days per year that each part of the contiguous United States would see average temperatures exceeding 86 degrees Fahrenheit (30 degrees Celsius) for at least 48 hours.
For example, if the average temperature exceeds 86 degrees for three consecutive days in June, and then again for five consecutive days in July, that counts as eight days total.
An average temperature of 86 degrees indicates highs during the day and lows during the night, depriving electrical equipment of the opportunity to cool. What’s even hotter is that most power adapters are not designed to operate at full capacity.
Although they often go unnoticed, there are more than 60 million transformers in the United States, mounted atop poles or locked inside steel cabinets placed on concrete pads.
Amid a heat wave in the Pacific Northwest in 2021, Avista Utilities, the power company in Spokane, Washington, cut power to tens of thousands of people, fearing its overheated transformers would explode. During that heat wave, 19 people died from heat exposure in Spokane County alone, with more than 1,000 deaths in total.
The analysis found that Phoenix would endure an estimated 126 days each year with heat that reduces transformer performance. Power outages during a heatwave would kill thousands of people in the city, according to a peer-reviewed study published last year.
By 2050, Washington, DCyou will encounter 13 days of heat waves stress transformers, 11 days more than at the turn of the century.
Note: “Baseline” is average annual days from 1981 to 2010. “Mid-century” is average annual days from 2036 to 2065.
Some cities will experience significant increases in the number of days with temperatures high enough to overheat transformers and cause power outages. ICF researchers used a baseline at the turn of the 21st century as a point of comparison. The average temperature in the contiguous United States is about 1.5°F (0.8°C) higher today.
Austin will experience about 83 heat wave days per year by mid-century compared to just 30 days during the baseline period, according to the analysis. New Orleans, Oklahoma City, Miami and Memphis will all face an extra month each year due to heat waves that will stress transformers.
ICF’s research only takes into account temperatures that tax transformers, but every component of the electric grid suffers during heat waves that last for days.
“When it’s hotter outside, our power plants are less efficient, our transmission lines are less efficient, and our air conditioners are less efficient,” says Michael Weber, a professor of mechanical engineering at the University of Texas at Austin and author of “When it’s hotter outside, our power plants are less efficient, our transmission lines are less efficient, and our air conditioners are less efficient.” Power Trip: The Story of Power.
The extent of damage during a heat wave depends on how poorly the network is performing. Frequent power outages can cause discomfort, “but it turns into a humanitarian crisis very quickly if the power goes out because it gets dangerously hot,” Weber said, adding that people who use dialysis equipment or rely on refrigerated medications are particularly at risk. .
Energy companies in places that don’t currently experience multi-day heatwaves will have to learn to adapt.
New York City, for example, will see two to 12 days of average heat a year that will be hot enough to damage transformers. Con Edison, the city’s electric utility, recently conducted a climate change vulnerabilities study and reported that “higher temperatures can reduce the capacity of cables, substation transformers and other equipment.”
In California, coastal cities like Los Angeles and San Diego will be spared heat waves that last for days because the ocean air cools them at night. But inland cities like Lancaster and Victorville, home to more than 300,000 people combined, will see weeks of heat waves annually.
Power company Southern California Edison recently warned that climate change will make existing infrastructure less efficient, especially in inland areas, leading to reduced capacity on lines and increased losses in transformers.
ICF’s research does not take into account how higher temperatures lead to increased electricity use, which increases pressure on the electric grid. During heat waves, energy demand rises because people turn on their air conditioners. In New York and Phoenix, for example, energy use is more than twice as high on the hottest days of the year than on moderate days.
Note: Chart shows every day from 2020 through 2023.
To make their transformers more heat-resistant, power companies can install cooling systems and try to place them in the shade. But the main thing to do is simply build more of them, electric company officials told me. More transformers means less electricity flowing through each transformer. It also ensures there are backup transformers in case one breaks down.
Electricity companies will also need more inverters to keep up with growing demand from power-hungry data centers and the growing movement to power everything from vehicles to stoves to heaters. By 2050, the United States will need three times as many inverters as it does now, according to a recent study by the National Renewable Energy Laboratory.
When people think of electricity, they mostly think of power plants that generate electricity or tools and machines that consume it, with little attention to what happens in between.
But if the grid of the future fails to meet the country’s insatiable appetite for electricity, it will be because of insufficient poles, wires and transformers, says Kerry Baker, an assistant professor of engineering at the University of Colorado at Boulder.
“People think as long as we have enough power generation, things will be OK,” Baker said. “We will have more power outages, but that is because of the infrastructure. It is not able to get the power where it needs to go.”
Check out my work
The ICF Climate Center presented data from its analysis of heat waves that would strain power transformers. The researchers assumed that warming would remain at 3.6 degrees F (2 degrees C) above pre-industrial temperatures by mid-century, a halfway scenario (for the nerds, it’s SSP2-4.5). For the baseline period, the researchers took the average of the years from 1981 to 2010. For the mid-century period, the researchers used the average of the years from 2036 to 2065. You can find the data and the code I wrote to produce the map at This is an accounting notebook.
Daily maximum temperatures in New York and Phoenix are from Open-Meteo, and daily electricity demand values are from the US Energy Information Administration. The data and code you wrote to produce the scatter plot is there This is an accounting notebook.
You can use code and data to produce your own analyzes and graphs – and to ensure they are accurate. To get in touch, email me and my editor, Monica Olmano.