Air conditioning is firmly entrenched in modern U.S. lifestyles, with over 80% of all new houses being centrally heated and cooled. This trend will likely remain in place even as energy prices increase along with pressure to reduce global carbon emissions. Air conditioning has been the major factor behind the explosive growth of the Sunbelt in the south and southwest. Las Vegas, Phoenix, Houston, Miami and many other cities would be only small regional centers if not for the availability of air conditioning for businesses and residences. Air conditioning is becoming more accepted even in areas where it was previously shunned, such as parts of Europe which experienced the severe heat wave in 2002 that was responsible for the deaths of thousands. Given its prominence in our modern society, we must learn to use air conditioning in an intelligent and efficient manner so we can benefit from the quality of life it provides, but without bankrupting our energy resources and permanently altering our global environment.