A study published in the American Geophysical Union journal Earth’s Future projected that, in response to global temperature increases, household demand for summer air conditioning in the U.S. is likely to outpace capacity. Without expanded capacity or improved efficiency, the result will be prolonged blackouts during the peak summer heat. A temperature increase of 1.5° C (2.7° F) — 2° C above preindustrial levels — could push demand up 8% to 13%.

The current trajectory, because of human-caused emissions, is to exceed 1.5° C by the early 2030s, according to the 2021 assessment of the Intergovernmental Panel on Climate Change (IPCC).

While other research has studied the impacts of increasing future temperatures on annual electricity consumption, this new study is the first to specifically project residential air conditioning demand on a household basis on a broad scale. The study combines data collected from 2005 to 2019 by the U.S. Energy Information Administration (EIA) on air conditioning use by statistically representative households throughout the contiguous United States with observed and predicted air temperature as well as heat, humidity and discomfort indices. The study only projected changes in usage resulting from climate change and did not account for population increases, greater affluence or changes in behaviors that affect demand for air conditioning.

"We tried to isolate just the impact of climate change," said Renee Obringer, an environmental engineer at Penn State University and lead author of the new study. "If nothing changes, if we, as a society, refuse to adapt, if we don't match the efficiency demands, what would that mean?"

The study found that improvements in technology that increase efficiency by 1% to 8% would be needed to offset a two-degree global temperature rise without increased demand for electricity, based on existing state standards and the predicted demand increase. Arkansas, Louisiana and Oklahoma are on the high end.

"It's a pretty clear warning to all of us that we can't keep doing what we are doing or our energy system will break down in the next few decades, simply because of the summertime air conditioning," said Susanne Benz, a geographer and climate scientist at Dalhousie University in Halifax, Nova Scotia, who was not involved in the new study.

Power grids stretched to the limit with extreme electricity consumption

During heat waves, which present the greatest health risks, increased air conditioning use is at the level most likely to overload the power grid. This also tends to coincide with below peak electricity generation, further reducing capacity and prompting rolling blackouts, that will impact already vulnerable populations, according to Orbinger.

The largest demand increases will occur in the south and southwest, with high percentage increases also expected in the Midwest. Indiana and Ohio could see demand triple.

Grey shading the map of the contiguous U.S. shows baseline air conditioning consumption in kilowatt-hours per household, by state, from 2005 to 2019. Source: Obringer et al. 2021 Earth's Future, DOI: 10.1029/2021EF002434Grey shading the map of the contiguous U.S. shows baseline air conditioning consumption in kilowatt-hours per household, by state, from 2005 to 2019. Source: Obringer et al. 2021 Earth's Future, DOI: 10.1029/2021EF002434

The bar graphs show the predicted change in kilowatt-hour consumption per household, by state, as global climate crosses 1.5° C (blue) and 2.0° C (pink) thresholds above pre-industrial temperature averages. States shaded darker grey over the map of the contiguous US consumed more air conditioning during the baseline period from 2005 to 2019.

Source: Obringer et al. 2021 Earth’s Future, DOI: 10.1029/2021EF002434Source: Obringer et al. 2021 Earth’s Future, DOI: 10.1029/2021EF002434

Darker grey states will need larger technical improvements in cooling efficiency to offset increased demand in a climate that is 2.0° C warmer (percentage in black numerals). Blue bars compare the number of household-days without air conditioning by state or region, also represented as pie charts on the map, if power supply air conditioner efficiency remains at current levels.

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