'It's Really Hard to Cool Things': Air Conditioning in the Modern World

Tim Hartford talks to Derek Thompson of The Atlantic about his new book Fifty Inventions That Shaped the Modern Economy. Their conversation begins with the air conditioner, where in New York City print shop workers tired of watching the building’s heat and humidity ruining their prints until a young engineer named Willis Carrier created a method to cool air moving over metal coils filled with compressed ammonia.  

Derek Thompson: Humans wanted to keep cool long before Carrier’s invention. But it’s sort of pathetic how we tried to do it. You describe the early 19th-century business of New England companies shipping large carved ice cubes insulated with sawdust around the country. New England literally exported ice the way Georgia exports peaches. There were even shortages during mild winters—“ice famines.”

Tim Harford: It was really hard to cool things! Before the invention of air-conditioning, you had to take something that was very cold and move it to places that were hot. And there were fascinating problems. For example, when the bodies of water that supplied the ice, like lakes, started getting polluted, the pollutants would be trapped in the pieces of ice. When they melted at their destination, it filled the air with unpleasant smells.

Thompson: Truly, thank God for Willis Carrier. The global effects of air-conditioning that you describe are mind-blowing. Air-conditioning transformed cities’ skylines, allowing for tall glassy skyscrapers that didn’t broil people in the top floors. It transformed demographics, allowing for migration in the U.S. to the Sun Belt, to Atlanta and Phoenix. By allowing politically conservative retirees to move south and west, you quote the author Steven Johnson saying that air-conditioning elected Ronald Reagan.

Harford: Yes, and it’s key to have a global perspective, too. This didn’t just reshape America. Air-conditioning reshaped the world. Places like Singapore and Shanghai are miserable when they’re hot and humid, but today they are global metropolises. There are studies saying that human productivity peaks around 70 degrees. That means that air-conditioning made us more productive, but also, by creating density in Singapore, it allows people to work longer and keep making the world a rich place. There is also the dark side of air-conditioning. You cool the temperature inside, but these units are energy-hungry, and they contribute to global warming.

Since that time, the air conditioning industry has become big business in the United States. And big energy users.  From the Buildings Energy Data Book by the US Department of Energy

  • Air conditioning makes up 10 percent of all housing energy use in the US, falling behind heating (37 percent) and water heating (12 percent) and right ahead of lighting (9 percent). 
  • In the three decades before 2009, energy consumption in all buildings (homes and commercial) increased by nearly half.
  • Buildings now make up 41 percent of all US energy consumption. That’s compared to 30 percent of the industrial sector and 29 percent of the transportation sector.