A swamp cooler — the affectionate name for an evaporative cooler — can save you a bundle of money on your electricity bills when temperatures skyrocket during the hot summer months. Unlike an air conditioner, which relies on near-constant electrical energy to keep refrigerant moving through the condenser coils, a swamp cooler uses only the natural process of evaporation to make your home’s air colder. When an evaporative cooler does use electricity, it’s only to run a fan that pushes cool air into your room.

If you’re excited by the energy savings and sustainability that evaporative cooling provides, great! The trick to getting the most out of your evaporative cooler is to know how to use it. These systems don’t operate like regular air conditioning, so it pays to learn a few swamp cooler tips and tricks to make it work at peak efficiency.

Here’s what you need to know.

1. Use Your Swamp Cooler in a Dry Climate

Map of where evaporative or swamp coolers work best

The biggest mistake people make with their evaporative cooler is trying to use it on humid days. This will never work. The whole point of an evaporative cooler is to bring down the temperature by allowing a fresh water supply to dissipate into dry air. As water evaporates, it naturally lowers the temperature in that area, and this cold air is then blown where you need it by the system’s fan. This process is the same as sweating: damp skin cools in dry air, making your body cooler in the process.

If you’ve ever noticed how miserable you are on a humid day, it’s because your sweat is evaporating into the air — there’s already too much moisture for evaporation to happen efficiently. The same thing happens with an evaporative cooler: High humidity levels make it impossible for the swamp cooler to work well because the water just can’t evaporate quickly enough to bring down the air temperature.

The bottom line? Evaporative cooling works best in the arid climates found in the desert Southwest and parts of Texas and California.

2. Use Your Swamp Cooler Seasonally

If you live outside of the desert and still would like to give evaporative cooling a try, it’s best to stick with a portable evaporative cooler instead of a full house model. These small appliances make it easy to move your cooling from room to room as needed — and to put the appliance away when it’s too sticky outside for it to be useful.

In general, evaporative coolers work best when the relative humidity is around 70 percent. Once it’s above 75 percent, they lose effectiveness and can actually make things feel worse as they tend to make the air more damp. If you live in an area where humidity rises and falls regularly, keep an eye on the weather. You can use your swamp cooler on dry days as a way to keep your central air conditioning use to a minimum, which will help you save on your utility bills.

3. Open the Windows

Running an evaporative cooler means “unlearning” some things you know about traditional air conditioning. While an air conditioner is most efficient in a sealed and insulated environment, swamp coolers actually do best with a steady stream of fresh air. As you run a swamp cooler, it makes moist air in your home as water evaporates into the air. However, the more humid the air in your house is, the less effective your evaporative cooler will be. To solve this problem, keep a few windows cracked to let dry air in and damp air out. An inch or two of air space should be sufficient to create an effective cross breeze. You may need to experiment to find the right combination of open windows and correct positioning of the evaporative cooler to keep the air flow working, but this is crucial for making sure your house doesn’t start to feel clammy.

4. Run a Dehumidifier

If it’s just too hot to open the windows, you can add a dehumidifier to your cooling arsenal instead. A dehumidifier draws excess moisture out of the atmosphere and collects it in a water tank until you’re ready to empty it. A dehumidifier on its own can help your house feel cooler in the summer on a humid day, as it will make drier air that helps your body’s natural perspiration work more effectively. By the same principle, it can also give your swamp cooler a big boost in efficiency. For best results, place your dehumidifier near your evaporative cooler’s air intake grill. This will help make sure that the driest possible air flows across the cooling pads for excellent evaporation.

5. Cultivate a Green Thumb

Family making terrarium at home

Another way to reduce humidity in your home is to add houseplants that suck up all the extra moisture they can find. Many plants have evolved to satisfy some or most of their water needs through the air rather than the soil, so they can help keep your house a little drier, which will help your swamp cooler to do its thing. Try these varieties for best results:

  • • Cacti
  • • Succulents
  • • Yucca
  • • Euphorbia
  • • Aloe
  • • Bromeliads
  • • Air plants
  • • Peace lily
  • • Boston fern
  • • English ivy

6. Experiment With Positioning

Smaller, portable evaporative coolers are designed to chill only a single room at a time — not your whole house. Check how many square feet the unit is recommended for, and be sure to use it in a room that size for maximum efficiency. You may also want to position the swamp cooler so that the fan blows cool air directly toward your dining table or living sofa. This way, you’ll get the benefit of the coldest air being aimed directly at you, and you’ll also enjoy the breeze from the fan to cool your skin. Use the wheels on your portable unit and move your cooler around until you find the optimal spot for your home.

7. Prime the Pads First

When you first start your evaporative cooler, it needs time for the cooling pads to fully absorb the water. Once they are wet, they more easily wick water from the tank to stay wet, but it can take up to 15 minutes for them to become saturated at the outset. Fill the water reservoir and give the pads time to work before turning on the fan. This way, you won’t waste energy blowing hot air around before your machine has reached its full cooling capacity.

Pro Tip: Once the pads are soaked, top off your water reservoir before turning on the fan. This will allow you to keep the air cooler for as long as possible before you need a refill.

8. Use Cold Water

Though you might think that hot water would evaporate more quickly since it’s closer to the boiling point (at which water dissipates into the air really fast), cool to room temperature water actually works better. A physics study showed that 50-degree water (about what you’d get out of the cold tap on your kitchen sink) worked most efficiently in an evaporative cooler, while performance decreased the warmer the water got.

9. Skip the Ice

On the other hand, the effects of cold water are limited. While 50 degrees was the optimal temperature found in the study mentioned above, adding ice to bring water down into the 30s or 40s doesn’t help much. This is because the ice will have to melt before it can evaporate, and this takes time — meaning that you’re not actually improving the efficiency of the evaporation process, which is how most of your cooling occurs in this system.

Adding ice will give a quick burst of cool air right in front of the machine, though, so if you’re looking for a quick hit of colder air after a workout, you can give this a try —just don’t expect the ice to do much more to cool down the whole room than your water is already doing.

10. Maintain Your Cooler

dirty air conditioner filter hand pick up

Like any other appliance, a swamp cooler runs most efficiently when it’s properly cleaned and maintained. During high cooling season, make sure to inspect and clean your unit before using it for the first time in the summer and before putting it away for the winter. You’ll also want to do a mid-season inspection. When you do so, be sure to cover the following items on your maintenance checklist:

  • Wipe down the exterior
  • Vacuum air intake grills and fans
  • Wash out the water tank with a mild soap and water solution
  • Inspect cooling pads for cracks or mildew, replacing as needed

Before storing your evaporative cooler for winter, make sure the unit is thoroughly cleaned and all water completely drained from the system. Don’t pack it away until it’s had a chance to dry out thoroughly — including the cooling pads. Putting a damp unit into storage is a surefire way to end up with mildew and other problems next spring.

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