The Guardian has an interesting look at the growth in air conditioning usage both within the United States and internationally.
[W]orld sales in 2011 were up 13 percent over 2010, and that growth is expected to accelerate in coming decades.
By my very rough estimate, residential, commercial, and industrial air conditioning worldwide consumes at least one trillion kilowatt-hours of electricity annually. Vehicle air conditioners in the United States alone use 7 to 10 billion gallons of gasoline annually. And thanks largely to demand in warmer regions, it is possible that world consumption of energy for cooling could explode tenfold by 2050, giving climate change an unwelcome dose of extra momentum.
The United States has long consumed more energy each year for air conditioning than the rest of the world combined. In fact, we use more electricity for cooling than the entire continent of Africa, home to a billion people, consumes for all purposes. Between 1993 and 2005, with summers growing hotter and homes larger, energy consumed by residential air conditioning in the U.S. doubled, and it leaped another 20 percent by 2010. The climate impact of air conditioning our buildings and vehicles is now that of almost half a billion metric tons of carbon dioxide per year.
If the estimates made by the author (Stan Cook, who also writes for Yale's Environment 360) are correct, car air conditioning accounts for between 5 and 7 percent of the nation's entire 2011 gasoline usage. (The Energy Information Administration has a somewhat lower estimation of the amount of electricity spent on cooling -- some 479 billion kilowatt-hours -- though the excludes manufacturing.)