Water consumption is the trade-off for the energy savings of evaporative cooling. Understanding usage helps you budget and determine if it's worthwhile in your area.
Typical water usage:
| Cooler Size | Gallons per Hour | Daily (8 hrs) | Monthly |
|---|---|---|---|
| Small portable | 1-3 | 8-24 | 240-720 |
| Medium window | 3-7 | 24-56 | 720-1,680 |
| Large whole-house | 7-15 | 56-120 | 1,680-3,600 |
Factors affecting water use:
1. Temperature - Hotter days = more evaporation = more water 2. Humidity - Drier air evaporates more water 3. Cooler size - Larger CFM units use more water 4. Bleed-off valve - Adds 1-3 gallons/hour to prevent mineral buildup 5. Pad type - Rigid media pads may use slightly more water than aspen
Cost impact:
At average US water rates ($0.005-0.01 per gallon):
- Small cooler: $3-7/month
- Large whole-house: $10-25/month
Comparison to electricity savings:
Even with water costs, evaporative cooling costs 50-70% less than air conditioning:
| Evap Cooler | Central AC | |
|---|---|---|
| Electricity | $15-40/month | $150-350/month |
| Water | $10-25/month | $0 |
| Total | $25-65/month | $150-350/month |
Water conservation tips:
- Use a bleed-off valve instead of dumping and refilling
- Fix any leaks promptly
- Don't oversize your cooler
- Turn off when not needed
- Recirculate "gray water" from cooler to landscaping (check local codes)
Is the water worth it?
In most Southwest cities, the electricity savings far exceed the water costs. However, in areas with very expensive water or water restrictions, you should calculate your specific costs before committing to evaporative cooling.