If you ask an older relative if they have heard of an evaporative cooler, they may say no. But chances are they would recognize the idea behind the technology. Before air conditioning or other cooler types existed, people would sleep outside on a screened in porch to try to stay cool at night. They would often hang damp sheets over the screens in an attempt to cool the air. As the hot air passed through the sheet, it was cooled. And then the cool air would slowly circulate, relieving some of the heat for the sleepers.

The same idea exists today in the form of evaporative coolers. These machines are wonderful cooling mechanisms for people who live in hot, dry climates. They are also known by the name swamp coolers, but that can be misleading because they actually won't work at all in swampy, humid conditions. The name probably came from the way that evaporative coolers actually add humidity to the air. But in fact, evaporative coolers need dry, hot air to work because in order for the air to be cooled, it has to be able to pick up (evaporate) some of the water. If the air is already saturated, it won't pick up any more water and it won't be cooled.

Here's how evaporative coolers work; the machine is composed of a fan that pulls the hot dry air inside the cooler, where it is passed through damp pads. The pads are kept damp by a pump that circulates water through the machine. As the dry air picks up some of the water, its temperature drops, sometimes by as much as 30 degrees Fahrenheit, depending on the climate. The cooler air is then blown into the room. An added bonus of an evaporative cooler is that the pads that cool the air also filter it. As the air passes through the pads, dirt, dust, allergens and other pollutants are captured in the fibers of the pads. So you'll be breathing cleaner, cooler air.

If you're wondering why you should choose an evaporative cooler over a traditional air conditioner, there's one more reason we haven't covered yet. The cost to run an evaporative cooler can be as little as 1/10 the amount it costs to run an air conditioner. In fact, some community power companies in hot, dry climates will actually offer residents a rebate if they install an evaporative cooler because they recognize the effective, efficient cooling capabilities of the technology. Contact your local power company to see if they offer the rebates and ask if they have any information on the effectiveness of an evaporative cooler in your area.