Swamp cooler, or refrigerated air.

Phoenix is one of the few American cities where this is still a real question, and plenty of older Valley houses have both: a swamp cooler for the dry months and refrigerated air for the rest.

They are not competing versions of the same machine. They work on entirely different principles.

How each one actually works

Refrigerated air, which is what most of this site is about, moves heat. A compressor and a refrigerant circuit pick heat up inside the house and dump it outside. It also removes moisture as a side effect, and it works regardless of what the outdoor humidity is doing.

Evaporative cooling, the swamp cooler, uses the energy it takes to evaporate water. Hot dry air is pulled through wet pads, water evaporates, and the air leaving is cooler and much wetter. There is no compressor and no refrigerant. It is a fan, a pump, and some pads.

Why one dies in monsoon

Everything about evaporative cooling depends on the air being dry enough to take up more water.

In May, with a dew point in the thirties, a swamp cooler can drop air twenty degrees or more and feels wonderful. In August, with monsoon moisture in, the same machine on the same roof manages a fraction of that, and it is pumping humidity into a house that already feels sticky.

Nothing failed. The physics stopped cooperating.

The practical differences

Running cost. A swamp cooler is a fan and a pump, so it is dramatically cheaper to run than a compressor. That is the whole appeal.

Windows. A swamp cooler needs air to leave, so windows crack open. Refrigerated air needs the house sealed. Running both at once with the windows open is the common and expensive mistake.

Water. Evaporative cooling uses a meaningful amount of water, and in a drought state that is a real consideration.

Maintenance. Pads, a pump, a float valve, mineral scale, and a seasonal changeover. Refrigerated air asks for different things: coils, filters, a drain line.

The changeover. Houses with both need the switch made twice a year, and a changeover done wrong is a common source of autumn and spring complaints.

Which to run, and when

The usual Valley pattern: swamp cooler through the dry heat of April, May and early June, then refrigerated air from the point monsoon moisture arrives until it leaves in September.

If you are running both at the same time, you are paying a compressor to remove moisture another machine is adding, through open windows. Pick one.

What this site covers

The published price list covers refrigerated air: diagnostics, tune-ups, capacitors, contactors, drains, motors, thermostats. Evaporative equipment is a different machine and it is not on that list.

If you have both and the refrigerated side needs attention, that is straightforward. If the swamp cooler is the problem, call and ask rather than assuming, and you will get a straight answer about whether it is worth the drive.