Reflections, commentary and analysis from Consortium for Science, Policy and Outcomes at Arizona State University.
By Clark Miller
People are generally far more rational than our hyper-scientific culture is willing to acknowledge. Occasionally, however, faulty assumptions are so deeply built into even scientific ways of thinking that errors get perpetuated over and over without ever being examined.
So it is with the environmental costs of air conditioning. The latest analysis comes from Elisabeth Rosenthal of The New York Times, in an article titled “The Cost of Cool” (Aug. 18, 2012). “Air conditioning,” Rosenthal writes, poses “one of the world’s most vexing environmental quandaries.” But does it, really?
The argument that air conditioning is a major environmental problem stems from the belief that air conditioning consumes excessive energy. As Rosenthal observes, “Fact 2: Air conditioners draw copious energy.” (Foreshadowing: not so much.)
Underlying this belief is another one: air conditioning is sinful. Rosenthal continues, “Fact 3: Scientific studies increasingly show that health and productivity rise significantly if indoor temperature is cooled in hot weather.” Then comes the kicker: “So cooling is not just about comfort.” Notice the presumption implied in the last sentence: air conditioning has been, at least in the past, not about necessity but about feeling good. Moreover, those good feelings come with a cost—just like any good sin.
To paint air conditioning as a quandary, Rosenthal is trying to get us to see air conditioning as not just an expensive, environmentally damaging luxury available to rich people. Why? Because that’s the presumption inherent in US cultural attitudes. Leonard Jordan writes: “In the last half century, air conditioning has joined fireworks, swimming pools and charred hamburgers as a ubiquitous ingredient of an American summer.” Stan Cox has written a new book, Losing Our Cool: Uncomfortable Truths About Our Air-Conditioned World (and Finding New Ways to Get Through the Summer), in which he observes that air conditioning is not only bad for the environment but bad for our health, as well. Get outside in the summer! Everyone, it seems, would agree: air conditioning is a problem.
But are they right?
Let’s start with a new set of facts. Fact 1. In the United States, the average household uses five times as much energy for heating than for cooling, as Figure 1 attests. Let me repeat that: 5 times. And that’s just for space heating. If we add water heating, the total for heating comes to 63% of average household energy use. Space cooling use is only 9% of total. And refrigeration is only 4%. How can that be, you say? Partly, of course, these are averages. For folks in Florida and Arizona, they are unrepresentative. I can attest from my own bills that at least 50% of my energy costs, here in Phoenix, go to air conditioning. In most of the country, however, energy use for air conditioning is very low compared to energy use for heating.
Figure 1. Average US household energy use, by end use.
Fact 2: Energy use in high air conditioning states is significantly lower than in other states. Really? Yep. See Figure 2. DOE really does collect data about everything. The three lowest states in the country for average household energy consumption are CA, AZ, and FL. California is low because their state utility regulators have pushed energy efficiency for the past 40 years, reducing their consumption by enormous amounts. I can guarantee that we’ve had no such program here in Arizona. Why then are AZ and FL energy consumption so low?
Figure 2. Average household energy use in the US by state.
I think you can probably guess. In neither state do you need to heat your house in the winter. That’s right, for all of you who think—and I used to think this myself—that air conditioning is an energy hog. It’s not, at least not when you compare it to heating. My utility bills are significantly lower in AZ than they were back in Wisconsin, thanks to the fact that my energy use has declined significantly, even with Phoenix summers. Note, in Figure 2, where the greatest energy use takes place: IL, NJ, MI, IA, MN, ND, SD, CT, ME, NH, RI, VT, ID, MT, UT, WY. I’ve lived in IL, IA, MN, and WY. Talk about places that are cold! Our northern tier states, especially those at high altitudes or that get their winter weather in the form of Arctic air masses out of Canada, have the greatest energy consumption.
How can that possibly be? Well, I’ll give you a hint. Even when it’s 117 outside, I am only cooling my house about 40 degrees, to 77. In Wisconsin, when I heated my house in the winter, I often had to heat from 0 to 68 (if I was really good and didn’t turn it up to 72). And on the worst days, it was -10 outside. In other words, the temperature difference I’m trying to make up for in Arizona on the worst days (40 degrees) is only about 50% of the temperature difference I was trying to make up for in Wisconsin on their worst days (78 degrees). That’s a really big deal, since energy use and temperature difference go hand-in-hand. The greater the temperature difference, the greater the energy required to maintain it over time.
But wait, you say: “That’s not fair. Heating is required for survival; air conditioning is not.” Now we get to the nub of it. Aside from the fact that 117 is brutal, by any definition, and can be quite deadly, think about the origins of our views about heating and cooling. Humans have heated their environments for millennia, because fire was an easily available tool. Air conditioning came along much later. Thus, we tend unconciously to take heating for granted and to think of cooling as a novelty. Worse, in the US, most of us migrated from Europe (and, even, Northern Europe), where cold temperatures predominate, as they do in much of the US. Moreover, since we view Arizona and Florida as places where rich people go to retire (this turns out to be largely a myth, too), we are culturally programmed to think of air conditioning as a luxury.
Take Andrew Ross’s new book, Bird on Fire: Lessons from the World’s Least Sustainable City. That would be Phoenix. And why, in Ross’s mind, is Phoenix unsustainable? Because it’s on fire. It’s hot, here, and that means we use a lot of air conditioning to cool our houses. Indeed, it’s fair to say Phoenix could not have reached the size and scale that it has without air conditioning. Not enough people would have been willing to move here. Now, don’t get me wrong. There are a lot of aspects of Phoenix that are highly unsustainable. But air conditioning isn’t one of them. If the 5 million people currently living in Phoenix and Tucson were, say, living in Detroit or Minneapolis, they would be consuming far more energy. (They would drive more miles on average on their daily commutes, too, according to the US Department of Transportation.) Dare we say that their lifestyles would be less sustainable, at least in terms of energy use?
Is there, in fact, any legitimate moral ground for differentiating between heating or cooling a house to a temperature that is comfortable for the people that live there? I’m afraid I can’t come up with one.
Indeed, if the subject is renewable energy, then cooling has some advantages, at least with respect to solar energy. Both heating and cooling occur on a 24-hour basis, especially in very hot and very cold environments. The greatest need for heating, however, is in the winter, often at night, when temperatures are the coldest. By contrast, the greatest need for cooling is in the summer, during the daytime, when temperatures are the hottest. Solar energy, which must ultimately provide the bulk of renewable energy, is more broadly available during summer days than during winter nights. It will be easier, therefore, to satisfy cooling needs with solar energy than it will be to satisfy heating needs. It’s not an accident that many households in Southern California and Arizona are putting solar panels on their rooftops.
One final observation: one of the sad features of the air conditioning story, at least as it is currently being told, is that it plays once again into unjust narratives about who is to blame for global warming. Rosenthal’s latest article is part of a series of articles she has written for The New York Times on the topic, all of which put the blame for global warming on rising demand for air conditioning in poor countries like India. In an article under the headline, “Chilling Effect: Relief in Every Window, but Global Worry, Too,” Rosenthal writes:
“In the ramshackle apartment blocks and sooty concrete homes that line the dusty roads of urban India, there is a new status symbol on proud display. An air-conditioner has become a sign of middle-class status in developing nations, a must-have dowry item. … But as air-conditioners sprout from windows and storefronts across the world, scientists are becoming increasingly alarmed about the impact of the gases on which they run. All are potent agents of global warming.”
It is worth remembering that, in India, per capita greenhouse gas emissions are approximately 10% of US totals, while 400 million people are completely without electricity. Over the next half century, air conditioners may, indeed, raise global greenhouse gas emissions totals—but I am willing to bet that, on a per household basis, they will never be responsible for as much of a long-term contribution to climate change as US households burning fuel oil or natural gas to heat their houses. Based on one study, space heating runs about 8000 kWh of energy use per year on average in the US. A modest-sized room air conditioner, drawing 7.5 amps, running 10 hours per day, for 100 days, would use about 800 kWh per year.
The bottom line: if you want to worry about the global warming consequences of personal comfort, worry first about heating, not cooling.
Clark Miller is the associate director for the Consortium for Science, Policy and Outcomes at Arizona State University.