And unlike AC units that work best in closed spaces, evaporative coolers actually shine in outdoor settings, making them perfect for cooling down patios, open garages, and workshops. Read my reviews of the best evaporative coolers available, as well as important factors to consider when choosing the right one for your specific needs. For indoor spaces, evaporative coolers perform best in areas with humidity levels at or below 30 percent, which typically applies to the Western and Southwestern United States. Placement and AirflowUnlike traditional air conditioners that recirculate and cool the same air in an enclosed space, evaporative coolers work by continuously drawing in fresh outside air, cooling it, and pushing it outward. For optimal performance, position your evaporative cooler near a window or door where it can draw in fresh, dry air.