AC vs. Evaporative Cooler
In dry climates a swamp cooler runs on about one-fourth the electricity of central AC. Compare annual operating costs — power and water — for your home and climate, including the honest answer for humid regions.
In a dry climate, an evaporative (swamp) cooler runs on about one-fourth the electricity of central AC — the catch is that it only works where summer air is dry, and it drinks water. Compare the annual operating costs for your home, with the climate honesty built in.
Home size
The cooled floor area in square feet. Both systems' costs scale with it — more space means more cooling load for AC and a bigger cooler moving more air (and evaporating more water) for the swamp cooler.
Your summer climate
The deciding input. Evaporative cooling only works where summer air is dry — it cools by evaporating water into the air, and humid air can't absorb more. Mild dry is high desert with short summers (Santa Fe). Moderate dry is a full but not extreme dry season (Albuquerque, Denver). Hot desert is a long, intense season (Phoenix, Las Vegas, El Paso). If your summers are humid — the East, South, Midwest — a swamp cooler will just make your house damp, and the calculator will tell you so.
Electricity rate
Your price per kilowatt-hour from a recent bill. The 2026 U.S. residential average is about $0.19/kWh, though many Southwest utilities run lower — and summer time-of-use rates in desert cities can run higher exactly when cooling matters.
Evaporative cooling wins in your climate
$242/yr saved
evap ≈ $129/yr (power + water) vs central AC ≈ $371/yr
Why it's so cheap — and what you trade for it
A swamp cooler is just a fan and a small pump — no compressor, which is where AC's electricity goes. The trades: it adds humidity (that's how it works), it needs open windows to push air through the house (the opposite of AC's sealed envelope), and it can only get you ~20–30°F below the outdoor temperature. Many desert homes run both: the cooler for most of the season, AC for monsoon weeks when the humidity spikes and evap fades.
The water is cheap in dollars — count it anyway
Your cooler would evaporate roughly 7,261 gallons a year — only ~$36 on the bill, but a real consideration in drought-restricted areas (and a bleed-off valve, which many coolers run to control mineral buildup, adds ~50% to it). Budget maintenance too: pads, a spring start-up, and winterization are part of swamp-cooler ownership.
AC cost = climate-typical annual cooling kWh for your size × your rate. Evaporative cost = one-fourth of the AC electricity (per DOE) plus water, scaled from DOE/PNNL's published usage for a 1,500 sq ft home (≈$5 per 1,000 gallons). Operating costs only — a swamp cooler also costs less than half as much to install, but neither install price is modeled here. Estimates, not bills.
💡About this calculator▼
In the desert Southwest, the cheapest cold air in town comes from a machine most of the country has never used: the evaporative cooler, better known as a swamp cooler. The Department of Energy's numbers are striking — an evaporative cooler uses about one-fourth as much energy as central air conditioning and costs less than half as much to install. For a home in Albuquerque or Phoenix, that's hundreds of dollars a year in operating savings from a box on the roof containing little more than a fan, a pump, and wet pads.
The physics is the reason for both the savings and the catch. A swamp cooler works by pulling hot, dry outdoor air through water-soaked pads — the water evaporates, the air cools 20–30°F, and a fan pushes it through the house. No compressor, no refrigerant, and the compressor is where AC's electricity goes. But evaporation only works when the air is thirsty: in humid climates, the air can't absorb more water, and a swamp cooler delivers little cooling and a clammy house. DOE's rule of thumb draws the line at summer wet-bulb temperatures of 70°F or lower — the deserts, the high plains, the intermountain West. East of that line, this comparison has an honest one-word answer: AC.
This calculator prices both systems for your home — and it's built around that honesty. Pick a dry-climate tier (modeled on DOE's own example cities, from mild Santa Fe to hot Las Cruces) and you'll get the annual electricity for each system plus the line item most comparisons skip: water. A swamp cooler for a 1,500-square-foot home evaporates roughly 3,000 to 12,500 gallons a year depending on climate — only $15–$62 at typical water rates, but a genuine consideration where drought restrictions live. Pick the humid option, and instead of a fake comparison you'll get the real answer and the reasons.
One more thing worth knowing before the numbers: many desert households don't choose — they run the swamp cooler for most of the season and switch to AC for the monsoon weeks when humidity spikes and evaporative cooling fades. The two-system strategy is common precisely because the operating-cost gap is this large.
Both systems priced for your home size and climate, plus the water line for the cooler.
Central AC = your square footage × a climate-typical annual cooling intensity: • Mild dry (high desert) ≈ 0.7 kWh/sq ft·yr · Moderate dry ≈ 1.3 · Hot desert ≈ 2.5 · Humid ≈ 1.8 …× your electricity rate. (Tiers are calibrated to bracket EIA's national residential AC data — a 1,500 sq ft home spans ~1,050–3,750 kWh/yr across them.)
Evaporative cooler: • Electricity = one-fourth of the AC figure — the DOE/PNNL ratio, applied directly • + Water, scaled from DOE/PNNL's published annual use for a 1,500 sq ft home: ≈2,980 gallons in a Santa Fe-like climate, 7,261 in an Albuquerque-like one, 12,457 in a Las Cruces-like desert — at ≈$5 per 1,000 gallons
The humid gate: choose a humid summer climate and the calculator doesn't print an evap number at all — evaporative cooling physically can't do the job there (DOE: suitable where wet-bulb temperatures run ≤70°F), so you get the AC estimate and the explanation instead.
Example — 1,500 sq ft, Albuquerque-like climate, 19¢/kWh: AC ≈ 1,950 kWh → $370/yr. Swamp cooler ≈ 488 kWh ($93) + 7,261 gallons ($36) → ≈$129/yr — about $240/yr saved, or roughly 65% off the cooling bill.
📐How it's calculated▼
AC $/yr = sqft × tier kWh/sqft × rate. Evap $/yr = (AC kWh × 0.25 × rate) + (tier gallons × sqft/1,500 × $0.005).
The sourced anchors: the 0.25 energy ratio (DOE: "one-fourth as much energy") and the water table (DOE/PNNL's 2,980 / 7,261 / 12,457 gallons for a 1,500 sq ft home across their three example cities — used verbatim as the three dry tiers).
Example — 2,000 sq ft in a hot desert (Phoenix-like), 19¢/kWh:
→ AC: 2,000 × 2.5 = 5,000 kWh × $0.19 = $950/yr → Evap electricity: 1,250 kWh × $0.19 = $238 → Evap water: 12,457 × (2,000/1,500) ≈ 16,600 gallons × $0.005 = $83 → Evap total ≈ $321/yr — saving ≈ $629/yr, every year, for as long as both systems run.
Example — the humid check: 1,500 sq ft humid-summer home → AC ≈ 2,700 kWh ≈ $513/yr, and no evap figure — because a number that can't be achieved shouldn't be printed.
📎Sources:DOE Building America Solution Center (PNNL) — Evaporative Cooling Systems: one-fourth the energy of central AC, less than half the install cost, dry-climate/wet-bulb suitability, and annual water use by climate,U.S. EIA — FAQ: air conditioning accounted for about 19% (254 billion kWh) of U.S. home electricity consumption (2020 RECS),U.S. EIA — Electric Power Monthly: average U.S. residential electricity price (18.83¢/kWh, April 2026)
🔍Finding your inputs▼
Home size: The cooled floor area in square feet. Both systems scale with it — a bigger house is more cooling load for the AC and a bigger cooler moving more air (and evaporating proportionally more water) on the evaporative side.
Your summer climate: The input that decides everything, so pick honestly. Mild dry is high-desert country with warm days and cool nights and a short season — Santa Fe, Flagstaff, much of the mountain West. Moderate dry is a full dry cooling season without extreme heat — Albuquerque, Denver, Boise, Salt Lake. Hot desert is the long, intense season — Phoenix, Las Vegas, Tucson, El Paso. Humid summer is everywhere the air feels heavy in July — the East Coast, South, Midwest, and Texas east of the dry line. The dividing question isn't temperature, it's moisture: evaporative cooling needs dry air to load with water vapor. DOE's threshold is a summer wet-bulb temperature of 70°F or lower — if you're not sure which side you're on, the muggy-summer test is honest enough, and choosing humid gets you a straight answer rather than a broken promise.
Electricity rate: Your price per kilowatt-hour from a recent bill. The 2026 U.S. residential average is about $0.19/kWh; many Southwest utilities run below it, but note that desert summer time-of-use plans can price peak afternoon power far higher — exactly when cooling runs hardest. If you're on time-of-use, your effective summer rate is the honest number to enter, and the swamp cooler's advantage grows with it.
⚠️Special situations▼
I live in Phoenix — why does everyone here have AC if swamp coolers are this much cheaper?
Because the desert's worst weeks are exactly the weeks a swamp cooler handles worst, and comfort in the extreme is what people buy cooling for. Phoenix summers have two personalities: the dry furnace of May and June — 105°F at 8% humidity, where evaporative cooling is at its absolute best, dropping air 25–30°F and costing pennies — and the monsoon season from roughly July through September, when dew points climb into the 50s and 60s. In that humid stretch, evaporative cooling fades badly: the air arrives at the pads already carrying moisture, the temperature drop shrinks to 10–15°F, and the cooler pushes warmish, damp air through a house that's 110°F outside. That's the failure mode that pushed metro Phoenix toward refrigerated air over the past few decades, along with sealed-house expectations (dust, allergies, security), two-story homes that duct poorly for cooler airflow, and HOA-era construction that simply stopped installing them. But note what the economics still say: for the majority of the cooling season, the cooler is dramatically cheaper to run, which is why the two-system strategy persists among cost-conscious desert households — evaporative cooling from April through June and again in October, refrigerated AC for the monsoon core. If your house already has both, running the cooler whenever dew points are low is close to free money at this calculator's ratios. If you're deciding on a new installation in the low desert, the honest advice is: a swamp cooler as your ONLY cooling is a genuine comfort gamble in the monsoon; a swamp cooler as your primary with AC as backup is the cost-optimized configuration; and AC-only is the convenience choice you pay a few hundred dollars a year for. Higher-elevation desert cities — Albuquerque, El Paso, Denver — tilt further toward the cooler, because their monsoons are shorter and their dry seasons longer.
What maintenance does a swamp cooler actually need? Nobody mentions this part.
More than an AC, on a seasonal rhythm — none of it is difficult, but skipping it is why swamp coolers get a musty reputation, and the honest annual budget is $50–$150 in parts plus a few hours of your time (or $100–$300 for a pro's spring service). The calendar: spring start-up means removing the winter cover, installing fresh pads, reconnecting the water line, checking the float valve, oiling the blower motor on older units, and testing the pump. The pads are the heart of it — aspen pads want replacing every season (sometimes twice in hard water), rigid cellulose pads every 3–5 years — because scaled, mineral-crusted pads block airflow and breed the swampy smell the machine is named for. Mid-season, the main enemy is mineral buildup: as water evaporates, its minerals stay behind and concentrate, coating pads and pan. The standard defense is a bleed-off valve that continuously discards a fraction of the mineral-concentrated water — effective, but it's why real-world water use runs about 50% above the evaporation-only figures (a factor this calculator's water line notes but doesn't add). In very hard water areas, pad life shortens and a drain-and-flush every few weeks helps. Fall shutdown matters more than people think: drain the water line and pan completely (freeze damage is the top killer of coolers and their plumbing), and cover the unit — an uncovered roof cooler is also a winter air leak straight into the house, worth real heating money. Compare all this with AC's maintenance — filter changes and an optional annual service — and the picture is: the swamp cooler trades a few hundred dollars a year of operating cost for a homeowner relationship. If you'll do the seasonal ritual (or pay for spring/fall service and still come out ahead), the economics hold. If a machine that needs remembering will not get remembered in your house, weigh that honestly — a neglected cooler cools poorly, smells, and wastes its own advantage.
Can I run a swamp cooler and keep my windows closed like AC?
No — and understanding why prevents the most common first-season mistake. An evaporative cooler is a once-through ventilation system, not a recirculating one: it continuously pushes outdoor air through the wet pads into the house, and that air must exit somewhere or the system chokes. Run it sealed and pressure builds, airflow collapses, humidity accumulates fast (all that evaporated water has nowhere to go), and within an hour the house is clammy and barely cooler — the exact experience that convinces people the machine 'doesn't work.' The operating rule: open windows a few inches on the far side of the house from the cooler, sized so air flows room to room and out — typically one to two square feet of opening per room being cooled, adjusted by feel (too little open = clammy; too much = the cool air short-circuits out the nearest window). This changes what living with one is like, and it cuts both ways. The upsides: continuous fresh air (a swamp-cooled house completely exchanges its air every few minutes — no staleness, great exhaust of cooking smells and indoor pollutants), and the evaporative-cooled air is filtered somewhat by the wet pads. The downsides: outdoor dust, pollen, smoke, and noise come along for the ride — a real problem during Western wildfire season, when running a swamp cooler pulls smoke indoors and the sealed-AC house wins decisively; allergy sufferers often prefer AC for the same reason; and open windows are open windows for security purposes (window stops that hold a 4-inch gap are standard practice). There's a refinement worth knowing: up-ducts — one-way ceiling vents into the attic — let some households run coolers with windows closed by exhausting into the attic (which also purges attic heat), a common retrofit in cooler-heavy regions. But the base fact stands: a swamp cooler is a flow-through machine. If a sealed, filtered, quiet envelope is non-negotiable for your household, that's a legitimate reason to pay AC's operating premium — this calculator tells you the size of that premium so you can decide what the sealed house is worth.
We're in a drought-restricted area — is a swamp cooler's water use irresponsible?
It's a fair question with a more interesting answer than it looks: in most of the arid West, the swamp cooler's water use is largely offset — sometimes exceeded — by the water your electricity would have consumed instead, so the environmental comparison is closer to a wash on water and a clear win on energy. The direct use first, honestly: this calculator shows roughly 3,000–12,500 gallons a year for a 1,500 sq ft home depending on climate (plus ~50% if running a bleed-off valve) — real water, roughly comparable to a few hundred toilet flushes a month or a modest garden. But electricity has a water footprint too: thermoelectric power plants (gas, coal, nuclear) evaporate cooling water per kilowatt-hour generated — commonly cited around 0.5–1 gallon per kWh consumed, varying with the grid mix. Run the trade for an Albuquerque-like home: the swamp cooler saves ~1,460 kWh a year versus AC, which at even 0.5 gal/kWh is ~730 gallons of power-plant water not evaporated — against ~7,300 gallons used at the house. So the honest statement is: the cooler uses more total water than AC in most grid mixes, but the gap is smaller than the household number suggests, and shrinks further on grids heavy with solar and wind (which consume almost no water). Meanwhile the energy saving is unambiguous — 75% less electricity is 75% less of everything electricity costs environmentally. Practical guidance for restricted areas: check your district's actual rules (most Western restrictions target irrigation, not evaporative cooling — some utilities actively encourage coolers for peak-demand reasons and offer rebates); maintain the unit well, since a poorly maintained cooler with a stuck float or excessive bleed can quietly double its water use — the responsible-use gap is mostly a maintenance gap; consider a thermostat kit so the cooler runs on demand rather than all day; and if water conscience is the deciding factor, note that the highest-efficiency modern AC or heat pump at low electricity rates is a defensible choice too. What's not defensible is guilt-canceling a cooler while irrigating a lawn — the lawn drinks more.
❓Common questions▼
How much cheaper is a swamp cooler to run than air conditioning?
About 65–75% cheaper in the climates where it works, which is among the largest operating-cost gaps between any two competing home systems. The foundation is the Department of Energy's figure: an evaporative cooler uses about one-fourth as much energy as central air conditioning, because it replaces the compressor — where AC's electricity goes — with nothing but a fan and a small water pump. In dollars, for a 1,500-square-foot home at the 2026 average electricity rate of about 19¢/kWh: in a moderate dry climate like Albuquerque, central AC runs roughly $370 a year against about $129 for a swamp cooler ($93 of electricity plus $36 of water) — a saving near $240 a year. In a hot desert like Phoenix or Las Vegas, a 2,000-square-foot home sees AC around $950 against roughly $320 for the cooler — over $600 a year. The saving repeats every cooling season for the life of the equipment, and the purchase side leans the same direction: DOE notes evaporative coolers cost less than half as much to install. Three honest qualifiers. First, the water: a cooler evaporates 3,000–12,500 gallons a year depending on climate and size — cheap in dollars (roughly $15–$62 at $5 per 1,000 gallons) but relevant in drought-restricted areas, and about 50% more if the unit runs a bleed-off valve. Second, climate is a hard gate, not a preference — in humid regions a swamp cooler simply can't deliver the cooling, so the comparison doesn't exist there. Third, the machines aren't comfort-equivalent even in the desert: the cooler fades during monsoon humidity, needs open windows, and adds moisture — which is why many desert homes run a cooler most of the season with AC for the humid weeks. Use the calculator above for your own size, climate tier, and rate.
Do evaporative coolers work in humid climates?
No — and this is physics, not product quality, so no brand or upgrade changes the answer. An evaporative cooler works by evaporating water into the air passing through its pads: the phase change absorbs heat, and the air comes out cooler. The process depends entirely on the air's capacity to absorb more moisture — dry air drinks eagerly and cools 20–30°F; humid air is already near its capacity, absorbs little, and cools barely at all. Worse, the machine still adds whatever moisture it can to your indoor air, so in a humid climate you get a small temperature drop plus a clammier house — the opposite of comfort, since humidity is much of what makes heat oppressive. The Department of Energy draws the usable line at climates where summer wet-bulb temperatures run 70°F or lower (functional with diminishing performance up to about 74°F) — in practice, the deserts and high plains of the West: Arizona, Nevada, New Mexico, Utah, Colorado, eastern Washington and Oregon, and West Texas. The East Coast, South, Midwest, and coastal Texas are firmly on the wrong side. A useful self-test: if your summer weather report regularly mentions dew points in the 60s and 70s, evaporative cooling is not for you; dew points in the 30s–50s, it will work well. Two caveats to the geography: even good evaporative country has humid interludes — the Southwest monsoon — during which coolers fade and households with both systems switch to AC; and 'evaporative coolers' sold as small indoor portable units are subject to the same physics, with the added problem that they recirculate humidified air in a closed room, which is why they disappoint nearly everyone outside the true dry zone. If you're in a humid region and want cheaper cooling, the real answers are a high-efficiency AC or heat pump, air sealing, attic insulation, and shade — our heat pump comparison calculator covers the biggest of those decisions.
How much water does a swamp cooler use?
Roughly 3,000 to 12,500 gallons per cooling season for a typical 1,500-square-foot home, depending almost entirely on how hot and long your cooling season is — that's the Department of Energy/PNNL's published range across three New Mexico example climates: about 2,980 gallons in mild high-desert Santa Fe, 7,261 in Albuquerque, and 12,457 in hotter Las Cruces. Scale those roughly with home size, and add about 50% if your cooler runs a bleed-off valve — the common accessory that continuously discards mineral-concentrated water to fight scale buildup, trading water for pad life. In everyday terms, hourly use runs a few gallons (commonly 3–10 gph while running), and the seasonal total lands somewhere between 'a few hundred extra toilet flushes' and 'a small garden.' In dollars it's minor: at a typical $5 per 1,000 gallons of municipal water, the seasonal water bill is roughly $15 to $62 — a rounding error against the hundreds of dollars of electricity the cooler saves. The gallons matter more than the dollars in two situations. In drought-restricted districts, evaporative cooling is real consumptive use worth checking against local rules (most restrictions target irrigation, and some utilities actually encourage coolers because they slash summer peak electricity demand — a few offer rebates). And for the environmentally minded, the full accounting is a trade: the cooler uses more water at your house but saves large amounts of electricity, and electricity has its own water footprint at thermoelectric power plants — narrowing, though not usually erasing, the household water gap, while the 75% energy saving stands. Ways to keep the water number honest: maintain the float valve (a stuck float quietly wastes water all season), size the bleed rate to your actual water hardness rather than wide open, use a thermostat kit so the cooler runs on demand, and replace pads on schedule — a well-maintained cooler is both the cheapest and the thriftiest version of itself.
Can I have both a swamp cooler and air conditioning?
Yes — the dual setup is common across the desert Southwest, and it's arguably the cost-optimized configuration for the region: evaporative cooling for the long dry majority of the season at one-fourth the energy, refrigerated AC for the monsoon weeks and extreme days when evaporation can't keep up. The operating pattern practically writes itself off the weather: dry 100°F days in May and June are swamp-cooler weather at its best; when July dew points climb and the cooler's discharge turns tepid and damp, you switch to AC until the air dries out again. Households that run this rhythm capture most of the calculator's savings — often several hundred dollars a season — while never gambling comfort on the muggiest week of the year. The practical cautions are about the changeover, and they matter: never run both systems at once. The swamp cooler needs open windows and pushes humid air through the house; the AC needs a sealed envelope and pays dearly to wring that added moisture back out — running both simultaneously makes each fight the other. Seasonal changeover should also be physical, not just thermostatic: when switching to AC, shut the cooler's water, and ideally damper or cover its duct — an open cooler duct is a hole in your sealed envelope that leaks conditioned air all summer and heated air all winter (the same reason winterizing the cooler with a cover is real heating-season money). If the two systems share ductwork, a proper barometric or manual damper at the cooler is the key piece of hardware; many setups instead duct the cooler to a central hallway and let the AC keep its own ducts, which sidesteps the conflict entirely. For a new installation, the incremental logic works like this: if you already own AC, adding a $1,500–$3,000 installed cooler that then does 70–80% of the cooling season's work pays for itself in a few desert summers at this calculator's savings rates; if you already own a cooler, adding AC is buying comfort insurance for the monsoon — dollars for certainty, which is a personal call the operating numbers can inform but not make.
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