If you live in a dry climate (below 50% summer humidity), an evaporative cooler will cool your home for 75–80% less electricity than air conditioning — saving $600–$1,000+ per cooling season. If your humidity regularly exceeds 50%, skip the swamp cooler entirely and go with AC; evaporative cooling simply doesn't work in humid air.
That's the fundamental split. But the full picture involves upfront costs, maintenance, water usage, installation complexity, air quality, and comfort preferences. This guide lays out every factor with real numbers so you can make the right call for your home and climate.
The Core Difference: How Each Technology Works
These two systems cool your home through completely different physical processes, and understanding that difference explains everything about when each one shines (or fails).
Evaporative Cooling (Swamp Cooler)
An evaporative cooler pulls hot outdoor air through water-soaked pads. As the water evaporates, it absorbs heat energy from the air, lowering its temperature. The cooled, now-humidified air flows into your home, and stale indoor air exits through open windows or vents.
Key physics: Evaporation only happens efficiently when there's a big gap between the current humidity and full saturation. Dry air = lots of evaporation = significant cooling. Humid air = little evaporation = barely any cooling.
Air Conditioning (Refrigerant Cycle)
An air conditioner uses a compressor to circulate refrigerant through a closed loop. The refrigerant absorbs heat from indoor air at the evaporator coil, carries it outside, and releases it at the condenser coil. This process also removes moisture from the air as a byproduct, lowering indoor humidity.
Key physics: The refrigerant cycle works regardless of outdoor humidity. Whether it's 10% or 90% relative humidity outside, an AC system produces cold, dehumidified air.
The fundamental trade-off: Evaporative coolers add moisture to your air; air conditioners remove it. This single fact determines which system works in your climate. In arid regions, the added humidity from a swamp cooler is actually a comfort benefit. In already-humid regions, it makes things worse.
Head-to-Head Comparison: Every Factor That Matters
Energy Consumption & Operating Costs
This is where evaporative coolers dominate — and it's not even close.
| Metric | Evaporative Cooler (3,500 CFM) | Window AC (8,000 BTU) | Portable AC (12,000 BTU) | Central AC (3-ton) |
|---|---|---|---|---|
| Wattage | 150–200 W | 700–900 W | 1,100–1,400 W | 3,000–3,500 W |
| Hourly electricity cost | $0.03 | $0.13 | $0.19 | $0.52 |
| Monthly cost (8 hrs/day) | $7.20 | $31.20 | $45.60 | $124.80 |
| Monthly cost (12 hrs/day) | $10.80 | $46.80 | $68.40 | $187.20 |
| 5-month season cost | $36–$54 | $156–$234 | $228–$342 | $624–$936 |
| Water cost (monthly) | $5–$15 | $0 | $0 | $0 |
| Total monthly operating | $12–$26 | $31–$47 | $46–$68 | $125–$187 |
Based on U.S. average electricity rate of $0.16/kWh and average water rate of $0.005/gallon.
Real-world comparison — Phoenix, AZ: The Hernandez family switched from a 3-ton central AC to a whole-house evaporative cooler for their 1,500 sq ft home. Their May–September electricity bills dropped from an average of $310/month to $55/month (including water costs). Annual savings: approximately $1,275. The cooler paid for itself in its first summer.
Cooling Performance by Climate
The critical question isn't which system cools better in general — it's which system cools better where you live.
| Climate Zone | Avg July RH | Evap Cooler Performance | AC Performance | Winner |
|---|---|---|---|---|
| Desert (Phoenix, Las Vegas, Palm Springs) | 10–20% | Drops temp 25–40°F | Standard cooling | Evaporative — far cheaper, effective |
| Mountain (Denver, SLC, Boise) | 15–30% | Drops temp 20–30°F | Standard cooling | Evaporative — great performance, huge savings |
| Great Plains (ABQ, El Paso, Lubbock) | 20–35% | Drops temp 15–25°F | Standard cooling | Evaporative — works well most days |
| Transitional (Sacramento, Fresno) | 25–45% | Works most days, struggles some | Consistent cooling | Hybrid approach — evap + AC backup |
| Upper Midwest (dry summer days) | 35–55% | Inconsistent; good some days | Consistent cooling | AC — evap too unreliable |
| Subtropical (Houston, Atlanta, Miami) | 60–80% | Nearly useless | Dehumidifies + cools | AC — no contest |
| Coastal (San Francisco, Seattle) | 50–70% | Poor performance | Effective when needed | AC — or just open windows |
Temperature Achievable: What Can You Realistically Expect?
Evaporative coolers don't have a thermostat in the traditional sense. They cool the air by a fixed amount based on the wet-bulb depression. Here's what different conditions actually produce:
| Outside Temp | Outside RH | Wet-Bulb Temp | Achievable Indoor Temp* | Temp Drop |
|---|---|---|---|---|
| 110°F | 10% | 75°F | 78–82°F | 28–32°F |
| 105°F | 15% | 77°F | 79–83°F | 22–26°F |
| 100°F | 20% | 78°F | 80–84°F | 16–20°F |
| 100°F | 30% | 82°F | 84–87°F | 13–16°F |
| 95°F | 25% | 79°F | 81–84°F | 11–14°F |
| 95°F | 40% | 83°F | 85–88°F | 7–10°F |
| 95°F | 50% | 86°F | 87–90°F | 5–8°F |
| 90°F | 35% | 80°F | 82–85°F | 5–8°F |
| 90°F | 50% | 82°F | 84–87°F | 3–6°F |
Assumes a quality cooler achieving 80–85% wet-bulb efficiency.
An air conditioner, by contrast, can typically achieve whatever indoor temperature you set — usually 68–76°F — regardless of outdoor conditions. The trade-off is the energy required to get there.
The 50% humidity wall: Notice how the achievable temperature drops off sharply once outdoor humidity passes 40–50%. At 50% RH, even on a 95°F day, your swamp cooler might only get you down to 87°F — barely comfortable. This is why we draw the line at 50% humidity for recommending evaporative cooling.
Upfront Costs & Installation
| System Type | Equipment Cost | Installation Cost | Total Upfront |
|---|---|---|---|
| Portable evap cooler (small) | $100–$200 | $0 (plug & play) | $100–$200 |
| Portable evap cooler (large) | $300–$500 | $0 (plug & play) | $300–$500 |
| Window-mount evap cooler | $400–$700 | $100–$300 (basic plumbing) | $500–$1,000 |
| Whole-house evap (roof/wall) | $800–$2,000 | $500–$1,500 | $1,300–$3,500 |
| Window AC unit | $150–$400 | $0–$100 | $150–$500 |
| Portable AC | $300–$700 | $0 (plug & vent) | $300–$700 |
| Mini-split AC | $1,500–$4,000 | $1,000–$3,000 | $2,500–$7,000 |
| Central AC | $3,000–$7,000 | $2,000–$5,000 | $5,000–$12,000 |
Portable evaporative coolers offer the lowest barrier to entry. You can have effective cooling for $150–$500 with zero installation. Central AC is the most expensive option upfront but offers the most comprehensive whole-home cooling.
Maintenance Comparison
| Maintenance Task | Evaporative Cooler | Air Conditioner |
|---|---|---|
| Pad/filter replacement | Every 1–5 seasons ($10–$80) | Every 1–3 months ($5–$30) |
| Cleaning | Weekly pad check, monthly deep clean | Monthly filter check, annual coil cleaning |
| Professional service | Optional — most DIY-friendly | Recommended annually ($100–$200) |
| Winterization | Required — drain, remove pads, cover | None needed for most systems |
| Typical annual maintenance cost | $30–$100 | $150–$400 |
| Common failure points | Pump, pads, water distribution | Compressor, capacitor, refrigerant leaks |
| Average lifespan | 10–15 years (window/roof mount) | 12–20 years (central), 8–12 years (window) |
| DIY repair difficulty | Easy — simple mechanical parts | Moderate to difficult — refrigerant requires licensed tech |
Real-world maintenance comparison: Tom in Albuquerque runs a window-mount evaporative cooler on his 1,200 sq ft home. His annual maintenance consists of replacing aspen pads ($20), a new pump every 3 years ($35), and 30 minutes of spring startup cleaning. Total annual cost: about $35. His neighbor with central AC spends $175/year on professional maintenance plus $60 in filters. Both systems are functioning well after 8 years.
Air Quality & Comfort
This is an area where AC has a meaningful advantage, and it's often overlooked.
Air conditioner advantages:
- Removes humidity, creating a drier, more comfortable feel
- Closed-window operation keeps out dust, pollen, and pollution
- Recirculates filtered indoor air
- Precise temperature control via thermostat
- Consistent comfort regardless of outdoor conditions
Evaporative cooler advantages:
- Adds humidity in arid climates (relieves dry skin, nosebleeds, static)
- Constant fresh air circulation — no "stale" recirculated air
- No refrigerant chemicals
- Doesn't create the "overly cold" feeling some people dislike about AC
Evaporative cooler disadvantages:
- Requires open windows — you can't seal your home against dust and allergens
- Added humidity can feel clammy if outdoor humidity spikes unexpectedly
- No precise temperature control; you get what the physics give you
- Can introduce outdoor odors (wildfire smoke, traffic, neighboring activities)
Allergy and asthma note: If you have respiratory conditions triggered by outdoor allergens, dust, or wildfire smoke, AC is the safer choice. Evaporative coolers constantly draw in outside air. During wildfire season in the West, this can significantly degrade indoor air quality. Some homeowners keep a backup AC window unit for smoke events specifically.
Environmental Impact
| Factor | Evaporative Cooler | Air Conditioner |
|---|---|---|
| Electricity use | 65–400 W | 700–3,500 W |
| Carbon footprint (electricity) | Very low | Moderate to high |
| Refrigerants | None | HFCs (high GWP) or newer R-32/R-454B |
| Water consumption | 3–15 gal/hour | None |
| Heat island contribution | Minimal (no heat rejection) | Yes (condenser dumps heat outside) |
| End-of-life disposal | Simple — metal and plastic | Requires refrigerant recovery |
In terms of total environmental impact, evaporative coolers win handily in most categories. Their electricity consumption is so low that even accounting for water use, the total environmental footprint is significantly smaller. The one exception: in areas with severe water scarcity, the 1,500–3,000 gallons/month of water consumption is a legitimate concern.
Total Cost of Ownership: 10-Year Comparison
Let's put it all together with a comprehensive 10-year cost analysis for cooling a 1,200 sq ft home in different climate scenarios.
Scenario 1: Phoenix, AZ (Ideal for Evaporative)
| Cost Category | Whole-House Evap Cooler | Central AC (14 SEER2) |
|---|---|---|
| Equipment + installation | $2,500 | $8,000 |
| Annual electricity | $100 | $1,100 |
| Annual water | $80 | $0 |
| Annual maintenance | $50 | $200 |
| Pad/filter replacements (annual) | $25 | $40 |
| Major repair (year 7 est.) | $150 | $800 |
| 10-year total | $5,200 | $21,400 |
| 10-year savings with evap | $16,200 | — |
Scenario 2: Denver, CO (Good for Evaporative)
| Cost Category | Whole-House Evap Cooler | Central AC (14 SEER2) |
|---|---|---|
| Equipment + installation | $2,500 | $8,000 |
| Annual electricity | $65 (shorter season) | $650 |
| Annual water | $50 | $0 |
| Annual maintenance | $50 | $200 |
| 10-year total | $4,350 | $16,500 |
| 10-year savings with evap | $12,150 | — |
Scenario 3: Houston, TX (Bad for Evaporative)
| Cost Category | Portable Evap Cooler | Window AC (8,000 BTU) |
|---|---|---|
| Equipment | $350 | $300 |
| Annual electricity | $45 | $250 |
| Annual water | $60 | $0 |
| Annual maintenance | $30 | $40 |
| Actual cooling achieved | Minimal — 3–5°F drop | Full cooling to set temp |
| Real value | Near zero — wasted money | Effective cooling |
The verdict on total cost: In suitable dry climates, an evaporative cooler saves $12,000–$16,000 over 10 years compared to central AC. Even compared to window AC units, the savings are $3,000–$5,000 over a decade. But in humid climates, buying an evaporative cooler is throwing money away — it won't effectively cool your space.
The Hybrid Approach: Best of Both Worlds
Some homeowners in transitional climates (Sacramento, Fresno, parts of Colorado and New Mexico) use both systems strategically:
How the hybrid approach works:
- May–June and September: Use the evaporative cooler exclusively (humidity is typically lower)
- July–August hot/dry days: Evaporative cooler handles it
- Monsoon season or humid spikes: Switch to AC for those specific days
- Evening/night: Often the evaporative cooler alone is sufficient even during humid periods
Real-world example: The Patel family in Tucson installed a roof-mount evaporative cooler ($2,200) alongside their existing 2.5-ton central AC. From May through September, they run the swamp cooler about 80% of the time and the AC about 20% (primarily during July monsoon humidity spikes). Their annual cooling cost dropped from $1,400 to about $450 — a 68% reduction.
Important rule: Never run both systems simultaneously in the same space. The AC removes moisture while the swamp cooler adds it, creating an energy-wasting tug of war.
Decision Framework: Which System Is Right for You?
Answer these questions to determine your best path:
Choose an evaporative cooler if:
- Your average July relative humidity is below 40% (ideal) or below 50% (workable)
- You live in the Desert Southwest, Mountain West, or Great Plains
- You're comfortable with windows cracked open while cooling
- You want the lowest possible operating costs
- You appreciate fresh air circulation and added humidity in dry climates
- You're handy enough for basic seasonal maintenance
Choose air conditioning if:
- Your average July relative humidity exceeds 50%
- You need precise temperature control (68°F exactly, every time)
- You have allergies, asthma, or sensitivity to outdoor air quality
- You want a sealed, quiet indoor environment
- Wildfire smoke is a regular concern in your area
- You're not interested in seasonal maintenance tasks
Consider a hybrid approach if:
- You're in a transitional climate zone (25–45% average summer humidity)
- You experience monsoon seasons with temporary humidity spikes
- You already have AC installed and want to reduce costs
- You want maximum comfort flexibility
Real-world decision example: Janet in Sacramento, CA was torn between the two systems. Her July humidity averages 35% but spikes to 55% during occasional heat waves. She installed a portable evaporative cooler ($380) as her primary cooling and kept her window AC unit as backup. She runs the swamp cooler about 25 days/month and the AC about 5 days. Her cooling bill dropped from $95/month to about $30/month.
Quick-Reference Comparison Chart
| Factor | Evaporative Cooler | Air Conditioner |
|---|---|---|
| Best climate | Dry (below 50% RH) | Any climate |
| Electricity use | 65–400 W | 700–3,500 W |
| Monthly operating cost | $10–$25 | $30–$200 |
| Upfront cost (portable) | $100–$500 | $150–$700 |
| Upfront cost (whole-house) | $1,300–$3,500 | $5,000–$12,000 |
| Temperature control | Approximate | Precise (thermostat) |
| Humidity effect | Adds moisture | Removes moisture |
| Air circulation | Fresh outdoor air | Recirculated indoor air |
| Windows | Must be open | Must be closed |
| Noise level | Moderate (fan + water) | Low to moderate |
| Maintenance | Easy DIY, seasonal | Professional recommended |
| Lifespan | 10–15 years | 12–20 years |
| Environmental impact | Very low (uses water) | Higher (refrigerant + electricity) |
Key Takeaways:
- Evaporative coolers cost 75–80% less to operate than AC — but only work in dry climates (below 50% humidity)
- Over 10 years, evaporative cooling saves $12,000–$16,000 vs. central AC in suitable climates
- AC provides precise temperature control, dehumidification, and sealed indoor air quality in any climate
- A hybrid approach (evap cooler + AC backup) can reduce cooling costs 40–68% in transitional climates
- The #1 deciding factor is your local humidity — check your average July relative humidity before buying either system
- Evaporative coolers require open windows; if outdoor air quality is a concern (allergies, wildfire smoke), AC is the safer choice