This is a question I've posted many times in many places, and to which I've never gotten an answer. I probably won't now, either!
I mentioned earlier...I think...that I live in Arizona. Southern Arizona, at that. This is an area that is hot pretty much nine months out of the year. Compared to the rest of the country, there is almost no rainfall. Water shortages are the norm here. Drought is also normal. That being said, the most popular method of cooling a home in this state is the evaporative, or swamp, cooler. For those not in the know, this is a box with pads on four sides with a pump constantly pumping water to the pads to saturate them. Air is sucked in through those wet pads and expelled into your house. This also means that everything in your house is slightly dampened by all the moisture in the air.
Now, when you start getting temperatures of 85 or better in late March, early April, the coolers start running. By the time "actual" summer arrives, the coolers are on twenty four hours a day, and will remain that way until November or December. Now remember, these pads are being constantly saturated with water. Imagine how much water goes through one cooler per year, then multiply that by at least one million! This, in a chronically water-short state! Yes, using swamp coolers is easier on your electric bill than air conditioning, but in the long run, what is really more expensive?
It gets better: the hottest months of the year, naturally, are July and August, which make up Arizona's "monsoon" season. What this means is that for these two months, the coolers are essentially useless, since they work by putting moisture back into the air. But since the humidity is up due to nearly daily rain, the coolers do nothing.
So now, after all of this, can someone tell me why these damn things are so popular?!