McCUTCHEON & SONS
PHOENIX HVAC & PLUMBING
Which Cools Cheaper?
(602) 837-3630
A swamp cooler can run a whole Phoenix summer on about a quarter of the electricity an AC pulls. It can also turn a July afternoon into a muggy, sticky mess the moment the monsoon rolls in. Which one is cheaper depends on which month you’re asking about.
Both machines cool the same square feet. They just do it in completely different ways, and the difference shows up on your bill, in your comfort, and in how much of your house you can actually use when it’s 110 outside.
They cool in two completely different ways
A swamp cooler, or evaporative cooler, pulls hot dry outside air through wet pads. The water evaporates, the evaporation absorbs heat, and the air that comes out the vent is cooler and wetter. It’s the same physics as stepping out of a pool into a breeze.
A refrigerated AC is a different machine entirely. It runs refrigerant through a coil to pull heat out of the air and dump it outside, and it strips moisture out of the indoor air as it works. One system relies on dry air. The other doesn’t care about humidity at all.
The electricity math is why people still love them
This is the number that keeps swamp coolers alive in Phoenix. According to the Department of Energy, an evaporative cooler costs about half as much to install as central AC and uses about a quarter of the energy, sometimes up to 75% less. One Phoenix homeowner told KJZZ his bills ran about $90 a month on a swamp cooler versus $320 a month after switching to AC.
That gap is real. A swamp cooler is essentially a fan, a pump, and some water, running maybe 3 to 15 gallons an hour. The water is a cost, but it doesn’t come close to eating the electricity savings. On paper, and on a dry April afternoon, the swamp cooler wins in a landslide.
The monsoon is the catch
Evaporative cooling only works when the air is dry enough to take the water. Here’s the drop you actually get, by humidity:
- Under 30% humidity: 18 to 25 degrees of cooling. Excellent.
- 30% to 40%: 12 to 18 degrees. Very good.
- 40% to 50%: 6 to 12 degrees. Marginal.
- Over 50%: under 6 degrees. You’re just adding mugginess.
Phoenix’s monsoon, roughly mid-June through September, drives the humidity straight into that bottom row, right when you need the cooling most. The same swamp cooler that felt great in May blows warm, sticky air in August. A refrigerated AC keeps working through all of it and dehumidifies the house while it’s at it.
What a swamp cooler can’t do
The savings come with trade-offs. A swamp cooler needs windows or vents cracked open to move air, so it doesn’t work with a sealed, well-insulated house. It doesn’t dehumidify, it adds moisture. It doesn’t filter the air the way an AC does. It needs regular maintenance: pads, mineral buildup, algae, and a winterizing routine every fall.
It also cools less precisely. On a 115-degree day, a swamp cooler that’s doing its best drops the air to somewhere in the 90s. Comfortable in moving air, but not the same as a set-and-forget 78.
The hybrid setup most Phoenix homes actually run
Here’s the pattern that’s been working in the Valley for decades. Run the swamp cooler through the dry shoulder months, April through June and September through October, and flip to refrigerated AC when the dew point climbs. You capture the cheap months and survive the sticky ones.
That’s why the honest answer to “which is cheaper” is “both, in the right season.” If you’re choosing one system for a year-round home, AC is the safer call. If you’re cooling a garage, a workshop, or a patio, or you already have AC and want to shave the dry-season bills, the swamp cooler earns its keep. The right choice starts with a straight read on your house, which is exactly what a second opinion is for.
The Department of Energy has a solid primer on evaporative coolers if you want the full spec sheet.
If that sounds like the company you’ve been searching for, we’re one call away.
McCutcheon & Sons is a family-owned and operated HVAC and plumbing company serving Phoenix and the east valley: Gilbert, Chandler, Mesa, Queen Creek, San Tan, Tempe, Maricopa, Scottsdale, and Fountain Hills. Since 1999, one name on the truck, the quote, and the door. Licensed #339149. No commissions, no hidden costs, guaranteed work.
McCutcheon & Sons Air Conditioning and Plumbing · (602) 837-3630 · mccutcheonandsons.com · AZ ROC License #339149