Climate Change Is Going to Seriously Crank Up the Air Conditioning

Electricity demand will get cranked up as well, by as much as 13%.

Air conditioners outside upscale apartment complex

Wendell and Carolyn / Getty Images

In the very first Treehugger article that I wrote about air conditioning back in 2006, I quoted author William Saletan, who defined the problem in "The Deluded World of Air Conditioning."

"Air conditioning takes indoor heat and pushes it outdoors. To do this, it uses energy, which increases production of greenhouse gases, which warm the atmosphere. From a cooling standpoint, the first transaction is a wash, and the second is a loss. We’re cooking our planet to refrigerate the diminishing part that’s still habitable."

That was in 2006 when average carbon dioxide levels were at 384.61 parts per million (ppm). In 2021 they were at 419 ppm, we are still cooking the planet, and according to a new study, "Implications of Increasing Household Air Conditioning Use Across the United States Under a Warming Climate," America is going to need either a lot more energy or a lot more efficiency.

The study, in its plain language summary—question: why doesn't every study have this? For that matter, why not write it all in plain language?—explains how it modeled changes in air conditioning demand at both 1.5 degrees Celsius (2.7 degrees Fahrenheit) and 2 degrees Celsius (3.6 degrees Fahrenheit) warming. According to the study: "In particular, households are projected to experience 8% more air conditioning after surpassing the 1.5°C threshold and up to 13% more after the 2.0°C threshold, when compared to the baseline (2005–2019)."

household air conditioning use
Household air conditioning use in the United States.

Obringer et al 2021

The study explains the image above: "Bar graphs show the predicted change in kilowatt-hour consumption per household, by state, as global climate crosses 1.5 degrees Celsius (blue) and 2.0 degrees Celsius (pink) thresholds above preindustrial temperature averages. States shaded darker grey over the map of the contiguous United States consumed more air conditioning during the baseline period from 2005-2019. Grey shading over the map of the contiguous United States shows baseline air conditioning consumption in kilowatt-hours per household, by state, from 2005-2019."

The largest increases in demand are in the South and Southwest. The study notes:

"If all Arizona households were to increase air conditioning use by the estimated 6% needed at 1.5 degrees Celsius of global warming, for example, amounting to 30 kilowatt-hours per month, this would place an additional 54.5 million kilowatt-hours of demand on the power grid monthly."

The biggest percentage increases are in the Midwestern states, where an increase of 2 degrees Celsius could triple demand.

The electrical system has to be designed to meet peak demand, which in much of the U.S. now happens in the summertime. The authors note if the efficiency of the air conditioning systems is not improved or the electrical supply increased, there will be significant numbers of days without power due to rolling blackouts. They seem to think that the efficiency improvements are achievable: "There has been an immense improvement of the equipment efficiency over the past several decades." The authors also believe policy and regulation changes can do it, without noting there is a huge installed base of existing equipment that is not going to be replaced for an 8% improvement.

The study authors concentrate on the improvement in the efficiency of air conditioning equipment to "maintain the status quo in terms of the electric supply." But that may not be enough given the focus of the study.

"It is important to note that these are the efficiency improvements needed to counteract the shifts in electricity demand only induced by climate change. To account for other factors that also influence demand (e.g., population growth, socioeconomic variables, etc.) additional efficiency gains will be necessary in order to effectively offset the demand increases."

“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, in the press release. “If nothing changes, if we, as a society, refuse to adapt, if we don’t match the efficiency demands, what would that mean?”  

But those other factors that influence demand are also a direct result of the warming climate. As Saletan noted in 2006, houses are changing in the face of warming.

"Instead of fixing the outdoors, we’re trying to escape it. On every street in my neighborhood, people have torn down ordinary homes and put up giant air-conditioned boxes that extend as far as possible toward the property line. They’ve lost yards and windows, but that’s the whole idea. Outdoor space is too hard to control, so we’re replacing it with indoor space. From 1991 to 2005, the median lot size of single-family homes sold in the United States shrank by 9 percent, but the median indoor square footage increased by 18 percent. If you can’t stand the heat, go hide in your kitchen."

There is also the issue of "heatpumpification." The authors note they do not see extreme increases in air conditioning demand in states like Oregon and Washington, but sales of central air conditioning systems are booming in the Northwest due to heatwaves and forest fires. Sales of heat pump systems are booming too, and these owners are going to find that the air conditioning that comes with them is very convenient in summer. It doesn't take long to become addicted to AC once you have it. It is too soon to tell, but it is likely that switching to pumping heat in during winter will lead to significantly more pumping heat out in summer.

The authors do note in passing that "there are a number of other factors that might lead to higher or lower air conditioning use than what was presented here," noting as an example that "improving insulation within houses can greatly reduce cooling needs." The authors add: "Future work can start to build off the climate impacts presented here to account for these different solutions, as well as behavioral or cultural changes that might further contribute to changes in the electricity consumed for air conditioning."

Given the dire data shown in this study, future work should be happening right now. Particularly in the south where the air conditioning demand growth is going to be greatest, there should be requirements for white reflective roofs, more rooftop solar, and a lot more trees. This is also a peak load problem, and peaks can be shaved or shifted by building our homes as thermal batteries with more insulation and other technologies such as phase changing storage devices. Or perhaps we should just not be building so much stuff in the first place. As Samuel Alexander, co-director of the Simplicity Institute, has written, efficiency without sufficiency is lost.

The authors also conclude with a note about equity, suggesting that it is the most vulnerable citizens who are affected most by the loss of power and air conditioning.

"In order to protect the most vulnerable citizens, it is crucial that we work to limit warming to 1.5°C above pre-industrial levels, while also working towards ensuring air conditioner efficiency improvements that may ultimately reduce the load on the electric grid. Hence, understanding the probable changes in electricity demand for air conditioning is a crucial step in preparing our electric power system."

With 1.5 degrees Celsius just a few years away, the implications of this report suggest we have to do a whole lot more than just improve air conditioning efficiency.

View Article Sources
  1. Obringer, Renee, et al. "Implications of Increasing Household Air Conditioning Use Across the United States Under a Warming Climate." Earth's Future, vol. 10, no. 1, 2022, doi:10.1029/2021ef002434