Temperature reduction from an evaporative cooler depends primarily on the humidity level of the incoming air. The drier the air, the more cooling you'll get.
Expected temperature drops by humidity level:
- Under 20% humidity (very dry): 20-30°F drop. This is ideal evaporative cooling weather.
- 20-30% humidity: 15-20°F drop. Still excellent performance.
- 30-40% humidity: 10-15°F drop. Good cooling, though not as dramatic.
- 40-50% humidity: 5-10°F drop. Marginal performance begins.
- Above 50% humidity: Less than 5°F drop. Evaporative cooling becomes ineffective.
For example, on a 100°F day with 15% humidity in Phoenix, an evaporative cooler can bring indoor temperatures down to 70-75°F. On the same temperature day during monsoon season with 50% humidity, you might only get down to 90-95°F.
Other factors affecting cooling performance:
- Cooler size (CFM) - Must be properly sized for your space
- Pad condition - Old or clogged pads reduce airflow and evaporation
- Ventilation - Proper exhaust is essential for maximum cooling
- Direct sunlight - Shaded areas stay cooler
- Home insulation - Well-insulated homes retain cool air better
