Swamp Cooler vs. Air Conditioning: Which Fits Your Phoenix-Area Home?

A swamp cooler, also called an evaporative cooler, cools your home by pulling outdoor air through wet pads. It then blows that cooled air through the house. Refrigerated air conditioning works a different way. It uses a refrigerant to carry heat out of your home, and it removes moisture from the air as it cools.

In the Phoenix area, the choice comes down to three questions. How does each system handle monsoon humidity? How much upkeep do you want? Would your home do better with one system or both?

We work on both swamp coolers and air conditioning systems in East Valley homes.

How a Swamp Cooler Cools Your Home

A swamp cooler is a fairly simple machine. The Department of Energy's guide to evaporative coolers describes a direct evaporative cooler as a box-like housing that holds a large blower fan and thick, sponge-like pads. The fan pulls in outside air and pushes it through the wet pads. As the air flows through, some of the water evaporates, and that lowers the air's temperature before it enters your home. In our technicians' experience, a swamp cooler can cool the air passing through it by up to about 20 degrees Fahrenheit. Because it cools with water, it also adds humidity to that air.

The biggest difference from air conditioning is where the air goes. Air from an evaporative cooler is not recirculated inside the house. Instead, it is blown through the house and needs a way to exit. Doors or windows must be opened to give it a path out, or ceiling exhaust vents can be installed instead.

Whenever a swamp cooler runs, it brings a steady stream of fresh outdoor air through your rooms. That is also why a swamp cooler can disappoint in a closed-up house. If the windows are shut and there are no exhaust vents, the cooler can't move air through the house the way it was designed to.

Swamp coolers can also be easy on energy use. Evaporative coolers can use far less energy than central air conditioners. The trade-off, as the next sections explain, is their dependence on dry air and on regular care of the water side of the unit.

Key Takeaway: A swamp cooler cools by evaporating water into outdoor air, and it needs an open window or an exhaust vent so that air can leave the house.

How Refrigerated Air Conditioning Works

Central air conditioning, often called refrigerated air, uses a refrigerant instead of water to do the cooling. A standard air conditioner uses a refrigerant to absorb unwanted heat in your home and transfer it to the air outside. At low pressure, the refrigerant absorbs heat from the indoor air and turns from a liquid into a gas. At high pressure, it passes that heat to the outdoor air and condenses back into a liquid.

While it cools, an air conditioner also removes humidity from the air. ENERGY STAR's room air conditioner guidance points out that a unit that is too large will cool the room before it has a chance to remove the humidity. The result is cool, moist air that makes the room feel damp and clammy. For a room unit, comfort depends on correct sizing, not only on the number on the thermostat.

Central systems also have a condensate drain, which is the line that carries water away from the indoor unit. That drain belongs on your maintenance checklist, because a plugged drain can cause water damage in the house and affect indoor humidity levels.

Why Does Monsoon Humidity Limit a Swamp Cooler?

Evaporative cooling depends on dry air. The Department of Energy's evaporative cooling guide says these coolers work best in dry climates where the outdoor relative humidity is low during the cooling season. It works through an example of hot, humid conditions in Sarasota, Florida. It concludes that under those conditions, an evaporative cooler would not work very well.

The monsoon is when this matters in the Valley. The National Weather Service office in Phoenix says monsoon season officially runs from June 15 through September 30. Its 2024 monsoon season review tracked that year's season over the same period. The review explains that during the monsoon, a reversal in the overall wind pattern results in a significant increase in atmospheric moisture across the southwestern U.S.

If you want to know how humid a monsoon day will feel, check the dew point. The dew point is the temperature the air would have to cool to before it became completely saturated with moisture. The higher the dew point rises, the greater the amount of moisture in the air.

The National Weather Service suggests checking the dew point instead of relative humidity to judge how dry or humid it will feel outside. When the dew point climbs, there is more moisture in the air, which is the opposite of the dry conditions evaporative coolers work best in.

Key Takeaway: Swamp coolers do their best work in dry air. The monsoon, which officially runs June 15 through September 30, brings a significant increase in moisture, so watch the dew point on those days.

Water Use and Upkeep for Each System

A swamp cooler needs a water supply to keep its pads wet, and minerals in that water can build up inside the unit. If your local water has a high mineral content, the Department of Energy's evaporative cooling guide describes two ways to handle it.

A bleed-off valve can drain off water to reduce mineral concentrations, but it can increase water use. An auto-flush system, also called a dump pump, is a more efficient option. It empties the cooler pan and brings in clean water at regular intervals to reduce mineral buildup.

Swamp coolers also need hands-on care at least twice a year. Spring start-up is the time to replace or clean the pads, check the belt for proper tension, and clean and inspect the cabinet for damage. At shutdown, shut off the water line and drain and clean the pan. Then install a winter cover to keep dirt and dust out of the unit.

Our swamp cooler maintenance and repair guide goes into more of the details. The Department of Energy's guide also gives an instruction about idle time. During the cooling season, the drain pan should be emptied whenever the cooler will be idle for more than a few days. Standing water left in the pan can become a breeding ground for mosquitoes and bacteria.

Refrigerated air doesn't need a water supply, but it has its own upkeep. ENERGY STAR recommends having a contractor do annual pre-season check-ups, with the cooling system checked in the spring. ENERGY STAR's maintenance checklist also includes cleaning the evaporator and condenser coils. Dirty coils reduce the system's ability to cool your home and cause it to run longer.

Key Takeaway: A swamp cooler can use less energy than central air, but it needs water and more hands-on care: a spring start-up, an end-of-season shutdown, and an empty pan whenever it will sit idle for more than a few days during the cooling season.

Can You Run Both in the Same Home?

Yes. Evaporative cooling can be used as a backup to traditional air conditioning or as the primary cooling for the home. In a home with both, the swamp cooler can handle the dry stretches of the year, and the refrigerated air can take over when monsoon humidity moves in.

Running both does mean looking after both. The swamp cooler still needs its water supply, its pads and its seasonal shutdown, and the air conditioner still needs its spring check. If your AC is aging and you're weighing whether to keep it as part of this decision, our AC repair vs. replace guide walks through that choice.

How to Decide What Fits Your Home

No single answer is right for every house. These questions can help you work out which system, or which mix of the two, fits the way you live:

• How does your household handle the humid part of summer? Refrigerated air removes humidity as it cools. A swamp cooler adds humidity to the air it cools, and it works best when the air is dry.
• Are you comfortable keeping windows open or adding exhaust vents? A swamp cooler needs a path for its air to leave the house.
• How do you feel about water use and hands-on upkeep? A swamp cooler needs a water supply, care at the start and end of each season, and, where the local water is high in minerals, a way to limit mineral buildup.
• Do you like fresh outdoor air moving through the house? A swamp cooler brings in a steady stream of it whenever it runs.
• How much does energy use matter to you? Evaporative coolers can use far less energy than central air conditioners.
• Would a backup make sense? A swamp cooler can serve as a home's main cooling or as a backup to air conditioning.

Key Takeaway: Decide based on how you handle monsoon humidity, how much water and seasonal upkeep you're willing to take on, and whether a swamp cooler as a backup to AC fits your home.

Frequently Asked Questions

Is a swamp cooler the same as an evaporative cooler?

Yes. The Department of Energy's guide to evaporative coolers notes that evaporative coolers were known in the past as swamp coolers. It describes a direct evaporative cooler as a unit with a blower fan that pulls outside air through wet, sponge-like pads. As the air flows through, some of the water evaporates. That lowers the air's temperature before it is blown into the house.

Does a swamp cooler work during monsoon season in Phoenix?

It still runs, but conditions work against it. The National Weather Service office in Phoenix says the monsoon brings a significant increase in atmospheric moisture across the southwestern U.S. The Department of Energy's guide says evaporative coolers work best in dry climates. On humid days, a swamp cooler may not keep your home as comfortable as it does when the air is dry.

Do I need to open windows when running a swamp cooler?

Yes, or you need ceiling exhaust vents. A swamp cooler blows fresh outdoor air through the house instead of recirculating the indoor air, so that air needs a way out. For the system to work correctly, doors or windows must be opened to give the air a path to exit. Ceiling exhaust vents can be installed instead.

Does an air conditioner remove humidity?

Yes. A refrigerated air conditioner removes moisture from the air as it cools. In its guidance on room air conditioners, ENERGY STAR points out that a unit that is too large will cool the room before it has a chance to remove the humidity. That can leave the room feeling damp and clammy, which is one reason correct sizing matters when a room unit is chosen.

Can a home have both a swamp cooler and air conditioning?

Yes. Evaporative cooling can be used as a backup to traditional air conditioning or as the primary cooling for the home. In a home with both, the swamp cooler can handle the dry stretches and the refrigerated air can take over when humidity rises. Each system still needs its own seasonal care.

What upkeep does a swamp cooler need compared with central air?

A swamp cooler needs care at the start and end of each season. The Department of Energy's guide lists replacing or cleaning the pads, checking the belt and cleaning the cabinet in the spring. At shutdown, it lists shutting off the water line, draining and cleaning the pan and installing a winter cover. For central air, ENERGY STAR recommends an annual pre-season check-up by a contractor, with the cooling system checked in the spring.

Why should I drain a swamp cooler that will sit idle?

Standing water is the concern. The Department of Energy's guide gives a clear instruction. During the cooling season, the drain pan should be emptied whenever the cooler will be idle for more than a few days. Standing water left in the pan can become a breeding ground for mosquitoes and bacteria.

Choosing the Right Cooling for Your Home

Swamp coolers and refrigerated air both have a place in Phoenix-area homes. A swamp cooler can use far less energy than central air, and it brings fresh outdoor air through the house. It also depends on dry air, and it needs regular care for its water, pads and pan. Refrigerated air cools with a refrigerant and removes humidity as it runs, which helps on muggy monsoon days. It also needs its own yearly check-up.

The off-season is a good time to think this through, well before next summer's heat arrives. To talk through the options for your house, call us at (480) 689-5167 or request a free estimate. We'll give you a straight answer, with no pressure.