For most Phoenix-metro homes, AC wins on year-round comfort. Swamp coolers cost less to run in dry months but lose effectiveness once monsoon humidity arrives, which is why most full-time homes have switched to AC while evaporative cooling holds on in garages, workshops, and drier parts of the state.

Running cost in dry months

Evaporative cooling is genuinely cheap to operate. A swamp cooler mostly draws power to run a fan and a small water pump, not to compress refrigerant, so electricity use is a fraction of what a comparable AC system pulls during May and June's low-humidity heat. Households running a swamp cooler as their primary cooling source through the driest stretch of the year typically see a noticeably smaller summer electric bill than an all-AC household of similar size.

That advantage is real, and it's the reason evaporative cooling never fully disappeared here despite AC being the dominant choice.

The monsoon problem

The advantage evaporates, so to speak, once humidity climbs. Evaporative cooling works by evaporating water into the air, and the process slows down hard as the air's own moisture content rises. A swamp cooler that drops the temperature 20 degrees in dry May air might only manage 8 to 10 degrees once monsoon humidity sets in around July and August, right when Arizona homes need cooling the most. AC doesn't have this weakness. A compressor-based system removes heat and moisture from the air by the same process regardless of how humid it already is outside.

This is the core reason swamp-cooler-only homes struggle for a chunk of the summer while AC-equipped homes don't.

Water use

Swamp coolers use water directly, continuously, for the entire cooling season. A typical residential unit can go through hundreds of gallons a week during peak summer operation, depending on size and how hard the water supply is (which affects how often the basin needs draining and refilling to manage mineral buildup). AC systems use essentially no water on the cooling side; their water use is limited to condensate drainage, which is a byproduct, not an input.

In a state where water policy and Colorado River allocations are an ongoing conversation, that difference matters to some homeowners more than the utility bill does.

Comfort ceiling

Evaporative cooling has a hard physical limit tied to humidity and outdoor temperature that AC doesn't share. Even in ideal dry conditions, a swamp cooler generally can't push a room below roughly 15 to 20 degrees under the outside temperature. On a 110°F day, that's still a hot house by most people's standards. AC can hold a consistent 75°F to 78°F regardless of how hot it is outside, within the limits of the equipment's capacity for the home's size.

Conversion costs

Homes still running an older evaporative-only setup sometimes ask about converting fully to AC. That usually means a new outdoor condenser, an air handler or coil added to the existing furnace if there is one, updated ductwork sized for AC airflow (swamp cooler ductwork is often undersized for AC by design), and new electrical circuits. It's closer to a full HVAC installation than a simple swap, so budget and plan accordingly rather than assuming it's a same-day project. Get a contractor to walk the existing ductwork before quoting, since duct sizing is the detail that most often turns a simple-sounding conversion into a bigger job.

The hybrid approach

Plenty of Arizona homeowners run both, deliberately. A house with central AC and a swamp cooler on a garage, workshop, or covered patio gets low-cost cooling for the space that doesn't need tight climate control, while the main house stays on AC for consistent comfort regardless of the season. Some older Phoenix-area homes still run a whole-house swamp cooler as a supplement during May and June specifically to cut AC runtime during the driest, least humid stretch of the year, switching over to AC once monsoon season arrives.

For anyone still running an evaporative unit, our guide to swamp cooler repair covers the parts that fail most and when it's worth fixing versus replacing.

Common questions

Is a swamp cooler cheaper to run than AC in Arizona?

Yes, during dry months. Evaporative cooling uses a fraction of the electricity a compressor-based AC system does. That advantage shrinks or disappears once monsoon humidity arrives in July and August, when a swamp cooler struggles to cool effectively regardless of how much it runs.

Can you use a swamp cooler and AC together?

Yes, and many Arizona homes do, typically with AC as the primary system and a swamp cooler covering a garage, workshop, or patio. Running both to cool the same enclosed space at once isn't effective, since a swamp cooler adds humidity that works against AC's dehumidifying function.

Why don't swamp coolers work well during monsoon season?

Evaporative cooling depends on dry air to work. As outdoor humidity rises during monsoon season, the air can absorb less added moisture, which sharply reduces how much cooling the unit produces. This is a physical limitation of the technology, not a sign of a broken unit.

Is it worth converting from a swamp cooler to full AC?

Often, yes, for a primary residence, since AC delivers consistent comfort regardless of humidity. The tradeoff is a higher upfront cost and usually some ductwork rework, since swamp cooler ductwork is typically undersized for AC airflow. Get a contractor to assess your existing ducts before budgeting the conversion.

Talk to a contractor before you decide

Troubleshooting an aging swamp cooler or pricing out a full AC conversion both start the same way: use the quote form below to compare licensed contractors near Mesa and Yuma before committing to either path.