Evaporative Coolers ("Swamp Coolers")

Evaporative Coolers ("Swamp Coolers")

Heating and cooling can account for up to 40% of your annual energy bill. In warmer climates, even a very efficient central air conditioner can cost you more than $150 per season to operate. As an alternative, an evaporative cooler (also called a swamp cooler) produces effective cooling by combining a natural process water evaporation with a simple, reliable air-moving system. Fresh outside air is pulled through water-saturated pads where it is cooled by evaporation and circulated through a house or building by a large blower. Using less than one-third the amount of electricity of an air conditioner, an evaporative cooler can lower the temperature of the air by up to 30F and deliver that air indoors to cool your home or building. Evaporative coolers cost half as much to purchase and install as an air conditioner.

Technology Options
Evaporative coolers work by utilizing a fan to pull hot, dry air through water-saturated pads. The air then causes water to evaporate off the pads, which causes the air temperature to decrease as its heat is transferred to the water. The cooled air is then blown into the building through a supply fan. Warmer air is forced out of the building through open windows or vents. To keep the pads wet, small distribution lines supply water to the top of the pads. Water soaks the pads and travels through them by gravity, collecting at the bottom of the unit in a sump where a pump recirculates the water to the pads. The evaporative pads can be made of wood or a synthetic material that absorbs and holds water while resisting mildew.

Small evaporative coolers can be installed in a window, blowing cooled air directly into a room. Larger units can blow air into a central location, or the air can travel through ductwork to individual rooms.

Evaporative coolers can work very well, provided the outside air they are drawing in is dry and desert-like. As the humidity increases, however, the ability for these units to cool the air effectively decreases.

Evaporative cooling offers an additional cooling benefit. The constant movement of the air created by the blower the cooling breeze it creates makes the occupants of a room feel 4F; to 6F cooler than the actual temperature. This is the same effect you feel when you turn on a ceiling fan or a window fan. For this reason, the "effective temperature" created by an evaporative cooler will feel 4F; to 6F cooler than temperature shown on the chart.

Efficiency Benefits
Evaporative coolers use up to 75% less electricity than air conditioning does. The Sacramento Municipal Utility District (SMUD) estimates the electricity savings at approximately $150 a year. For hotter desert climates, the savings can be much greater. Many people appreciate the fact that evaporative cooling adds moisture to the air, which helps to keep wood furniture, fabrics and plants from drying out, and helps keep you hydrated. The moist pads through which the outside air flows are also reasonably effective air filters, trapping some dust and pollen. Since the pads are continually wetted, trapped particles are flushed out and trapped in the bottom of the cooler.

(Neither this list, nor any mention of a specific vendor or product in this guide, constitutes an endorsement or recommendation of any vendor or product by Flex Your Power.)
and are some of the largest of more than 40 manufacturers of evaporative coolers and accessories.

Purchasing Tips

Evaluate your climate. An evaporative cooler will not work to effectively cool your building if the climate is too humid because they rely on hot dry air to evaporate the water in the evaporative pad. The California Energy Commission (CEC) provides a that plots optimum evaporative cooler operating temperatures and humidities.
Size your cooler. In order for your evaporative cooler to effectively do its job, it must be the proper size. They are rated by cubic feet per minute (CFMs). A simple formula is to take the area of the space that you want to cool and divide that number by two. That will give you the CFM rating for the proper-sized cooler.
Look for efficient fan motors. Although they use approximately one-third the electricity of an air conditioner, the fan may still use a considerable amount of electricity. Look for a model that is the most efficient.
Does the cooler have two speeds? An evaporative cooler should have at least two speeds and a vent-only option. During vent-only operation, the water pump does not operate and outside air is not humidified. This allows you to use the cooler as a whole house fan during mild weather.
Is the cooler covered? Make sure the cooler comes with a cover to insulate your home during the heating season.
Emerging Technology
Two-stage evaporative coolers have been developed that pre-cool the air before it goes through the moistened pad. The new coolers are reported to be as effective as air conditioning, but their initial cost is high about $5,000 for a whole-house system, approximately the same as air conditioning. The price may come down as more such systems are sold, but for now two-stage systems are hard to find and expensive.

There are now evaporative coolers on the market that use photovoltaic (PV) panels to create the electricity used to run the blower and the water pump. For hot, desert areas, the combination of evaporative cooling and solar power are a perfect match: the afternoon, when the most solar energy is available, is also the hottest part of the day, when cooling is most needed. And, since evaporative coolers use a fraction of the energy of air conditioners, PV cells can provide enough electricity to run the system effectively.