Evaporative coolers are a good cooling choice for hot-dry climates; but they are useless in humid climates and of little value in regions with cool summers and short cooling seasons.
But what about their use in some mixed climates: hot dry climates with several weeks of humidity, or moderate climates with large periods of hot weather?
That’s difficult to say. It depends on the specifics of the climate and on personal preferences.
There are, anyway, some fundamental choices and combinations - involving evaporative coolers, fans and air conditioners - that you may want to consider. They are important for energy savings and energy-efficiency. We list them below.
Evaporative coolers vs. AC
As already mentioned, it's in dry climates that evaporative coolers are cost-effective. They cool quickly, and are healthier and more efficient and greener than AC. Their installed costs are often 1/3 of central air conditioners, and their running costs about 1/3-1/4 or central AC.
But in regions where wet weather can last for weeks, evaporative coolers aren't a good or cost-effective choice. If you don’t mind to restrict cooling to some rooms, window air conditioners and ductless air conditioners (mini-splits) can be a better option.
In fact, window or ductless AC may cost less than an evaporative cooler and it works both in dry and wet weather conditions. You just need to implement the right cooling strategy, which can also involve the use of window fans for certain periods of time (to get breezes), or circulation fans to allow a higher air conditioning setting, to save energy…
But, as mentioned, that depends also the specifics of your climate, and on your preferences.
The economics of evaporative coolers
With the exception of low-cost portables, the prices of evaporative coolers are mostly in the range of $500 to $1,000, depending on the exact type of model and design .The installation costs may amount to $200 or $300+ for central units. On the other hand, they will consume about 1/4 of the electricity required by air conditioners.
Evaporative coolers vs. Fans
Fans, though with obvious limitations, can be a better cooling option than AC or evaporative coolers in many hot tropical climates.
Air conditioners are too expensive to be used extensively in hot tropical climates, where evaporative coolers are also inadequate due to high levels of moisture.
In such climates, a mix of fans, ventilation, and shading strategies - involving trees and roof cooling materials - are the better choice from an efficiency standpoint.
Mix low-Cost cooling strategies
In moderate and hot climates with long cooling seasons and diverse patterns of hot weather conditions, it can be advantageous to use a combination of methods. And evaporative coolers can be part of it, if there are significant periods of dry-hot weather conditions.
In other words: it can be cost-effective to combine the use of fans, evaporative coolers and air conditioners - and also shading and ventilation... You can use an evaporative cooler in the hot-dry periods, and its fan-only option to get evening and nighttime breezes (the fans of the evaporative coolers can work as a whole-house); and you can use one or more ceiling fans (or other circulation fans) with air conditioners to increase their temperature setting and to get energy savings, during wet weather.
Obviously, the use of such a diverse set of equipment has an overall cost that should be considered. Possibly, it's not cost-effective to use central air conditioners with a central evaporative cooling system… You have to consider their joint cost and the energy savings that they provide.
But, on the other hand, the overall cost of a system involving ceiling fans, an evaporative cooler and a window or a ductless AC system can be smaller than that of a central air conditioner… And they can replace the central AC system without significant loss of comfort, and with high electricity savings...