Keep cool without pricey AC

Advanced systems -- two-stage evaporative coolers such as those made by AdobeAir and Davis Energy Group's OASys -- employ a pre-cooler to extend the product's usefulness into hotter and more-humid conditions.

Making the decision

Coolers add humidity, so they shine where humidity is low. How low? A chart at the California Energy Commission's site shows optimum conditions to help you decide. A map at the Washington State University site marks the best regions (typically from the Rockies westward).

Should you buy a new evaporative cooler? That depends on your bills, your weather and the efficiency of the system you've already got. You might purchase a portable unit on a trial basis. Find them at home-improvement centers and chains such as Sears and Wal-Mart. They often sell out in heat waves, so call around to locate one, then check the store's return policy to ensure you could get a full refund. Learn how many days you have to return it and save your receipt. If the model you buy is noisy, try other brands.

Higher-end coolers require professional installation, so contact air-conditioning companies. They cost less than air conditioners and need no expensive professional maintenance, so providers are less motivated to carry them. You may have to phone around to find one.

Whole-house fans

Where nights are cooler, even during one or two seasons, a whole-house fan can whittle your electric bill. Their cost ranges from a few hundred dollars to more than $1,000 for the most expensive home units, with installation starting at around $300, more if attic venting is included. But it can shave 30% off your bill if you run it instead of air conditioning at night.

"At night you bring all this cool air into the house, then you close the house up in the day and you are living off the cool you got in the night," says Kirby, who used a whole-house fan while living in Missouri.

You'll need an attic because the point of the fan is to cool it off. It fits into the ceiling, usually in a hallway, and sucks hot air up and out attic vents. It can be quite effective.

Manny Robledo, in sweltering San Dimas, Calif., uses a whole-house fan. Returning home after a hot day, "you turn this thing on, and in a matter of 15 minutes you cool the house," he says.

Comparing costs

Here's how to compare the cost of operating your air conditioner with an evaporative cooler or whole-house fan:

• Estimate how many hours a month you run air conditioning.
• Check the label on your air conditioner to see how many kilowatts it uses. The label may not say, but it will show the amps and volts used, so calculate the number of watts it consumes by multiplying the amps (quantity of energy used) by the volts (pressure at which the energy is delivered) on the label. Divide by 1,000 for kilowatts.
• Multiple the kilowatts used by the number of hours you run air conditioning each month to find the kilowatt-hours it consumes monthly.
• Next, see what it's costing you to run the air conditioner by consulting your electric bill to find the cost of a kilowatt-hour of electricity. Multiple the cost by the number you arrived at for kilowatt-hours.
• Do the same for the new appliance.

If in doubt, remember: The savings from an energy-efficient appliance will increase over time. "The way utility costs are rising, savings could potentially grow," notes Katz, of Colton Electric Utility.

Updated May 27, 2008

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