Air conditioning can fail in the heat

Demand for air conditioning is booming, expected to triple worldwide by 2050 as global temperatures soar and incomes rise. The problem is that without electricity, people can’t use air conditioning. Many power grids are straining to breaking point as extreme weather becomes more common.

For example, when Hurricane Ida swept through Louisiana in August 2021 with high winds and severe flooding, more than a million people lost power. A heat wave followed. Temperatures soared above 90 degrees Fahrenheit (32.2 degrees Celsius), threatening residents who could not turn on their air conditioners due to days of power outages.

The combination of storms, heat waves, and multi-day power outages is a nightmare scenario, but one that will become increasingly common as humans continue to warm the planet, fueling more destructive extreme weather. It also reveals an uncomfortable truth about air conditioning, the solution to protecting people from the heat.

Weather accounted for 80% of major power outages in the U.S. from 2000 to 2023, according to a report from Climate Central, a nonprofit research organization. In the U.S., the aging power grid was designed for past weather conditions rather than future ones, said Michael Webber, a professor of mechanical engineering at the University of Texas at Austin.

The main threat is storms, which can knock down transmission lines and power poles. But heat waves also impact the grid. If it’s really hot outside, the system becomes less efficient. The grid can also be stressed by demand as people turn on their air conditioners to cope with the heat.

The number of major power outages in the U.S. (those affecting more than 50,000 customers and lasting at least an hour) doubled from 2017 to 2020, said Brian Stone Jr., a professor of urban planning and environmental design at the Georgia Institute of Technology. Much of the increase occurred during the summer months, he said.

A surge in cooling demand during California’s August 2020 heat wave prompted the state’s main grid operator to cut power to hundreds of thousands of homes in the first rolling blackouts in 20 years. In 2021, during a heat wave scorching the Pacific Northwest, electrical equipment overloaded, leading to rolling blackouts for tens of thousands of homes as temperatures rose above 100 degrees Fahrenheit.

In June 2024, when temperatures in southern Europe hit 40 degrees Celsius, parts of Albania, Bosnia, Croatia, and Montenegro experienced hours-long blackouts due to a spike in demand for electricity. Even short blackouts can be dangerous, according to Webber. Heat stress can damage vital organs and cause heat exhaustion, heat stroke, and even death. If the blackout is cold, people can simply put on more clothes, light a fire, and huddle together. If it’s hot, the only way to cool off is to use electricity. The combination of heat and blackouts is the most dangerous climate-related event, according to Stone.

Stone and a team of scientists explored the potential impact of heat waves accompanied by multi-day power outages due to extreme weather or cyberattacks. Focusing on Atlanta, Detroit, and Phoenix, they looked at what happens in people’s homes. The numbers are especially grim for Phoenix. During a heat wave with power outages lasting three to four days, half the city’s population (nearly 800,000 people) would be hospitalized for heat-related illnesses. More than 13,000 would die. The city’s climate is so extreme, Stone says, that residents struggle to adapt. Air conditioning could make people less resilient because they rely so heavily on cooling systems at home and at work.

Arizona Public Service, one of the energy companies that provides power to Phoenix, said it has plans in place to prevent large-scale outages and regularly maintains its grid. While the likelihood of a multi-day outage during a heat wave in Phoenix is ​​low, it is possible and could become more common as the climate crisis worsens. Cutting pollution that warms the planet is the best long-term defense against heat and extreme weather, Stone said.