03-28-2013, 06:28 PM
Since air conditioners are, in part, heat engines (they compress a gas, allow it to cool to about ambient, and then allow it to expand, which results in cooling), the overall efficiency of an air conditioner is relatively low. The difference between a Miami or Phoenix and a Minneapolis or Fargo, I think, is that the difference between the temperature extreme and what we think of as comfortable might go from 70 degrees in Minneapolis to maybe 18 degrees in Miami. In other words, if it is 98 degrees out, you only have to cool by 16 degrees to feel comfortable, but if it is minus 5, there is a much longer way to go. Figure that in Minneapolis, the temperature can be anywhere from near freezing to well below freezing for 4 months of the year, that is a lot of heat to provide.