Air Conditioner vs Evaporative Cooler vs Fan Comparison

Air Conditioner vs Evaporative Cooler vs Fan

Because of the potential for moisture build-up indoors, evapora­tive coolers are not recom­mend­ed for indoor use in humid climates.

Is it hot where you are right now? Does it get pretty warm during the summer? If so, there is a good chance you have a nice air conditioning unit. If not, perhaps you suffer through the heat, fanning yourself with booklets, stacks of paper, or anything else you can find.

There are different types of heat. Depending on altitude and proximity to the equator, heat can be dry or humid. This affects the efficiency of cooling devices. Mechanical methods of cooling down include air conditioning, evaporative (or swamp) coolers, and a variety of whirling blade fans. That is pretty much the order of cost and level of installation difficulty. But there are other considerations in making your choice.

Comparison Table

Air Con­diti­onerEvapora­tive coolerFan
Method of Cooling
Vapor-compression or absorption refrigeration cycles cools air.Water's large enthalpy of vaporization. The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation), which can cool air using much less energy than refrigeration.Circulates air to speed evaporation of the human sweat, thereby cooling our bodies.
Cost of Running
Cost of running is more than an evaporative cooler.Cost of running is less than typical air conditioners.Can be the least expensive cooling method. The size of blades, air purification filters, and ceiling mounts increase the cost.
Introduction (from Wikipedia)
An air conditioner is a device that lowers the air temperature. The cooling is typically achieved through a refrigeration cycle.An evaporative cooler (also swamp cooler, desert cooler, and wet air cooler) is a device that cools air through the evaporation of water.
Removes humidity from room.Adds humidity to room.Little effect on room humidity.
Requires outdoor vent.No outdoor vent is required but an open window can mitigate humidity buildup.Open windows may improve air circulation, particularly in humid regions.

Air Conditioners

A heating, ventilation, and air conditioning (HVAC) unit heats in the winter and cools in the summer. This is the top-of-the-line climate control for indoor spaces. HVAC units must be properly vented. Ducts, vents, and thermostats are professionally installed. HVAC is standard for most commercial offices—especially those that lack openable windows. Make certain you replace filters regularly to prevent mildew from triggering allergies.

This reminds me of a billboard I saw off the highway in Kentucky. The large headline is, “Your wife is hot.” The smaller text encourages you to buy her an air conditioner. Air conditioners dry the atmosphere as they chill it with coolant.

Your Wife Is Hot Billboard

If you want to spend less than the cost of HVAC, room air conditioners can be mounted in a window frame. Even smaller portable units on wheels can stand on the floor near a window for intake and exhaust vents.

Evaporative Coolers

The middle ground is comprised of evaporative coolers in a variety of different sizes. These may be used indoors or outdoors. Larger units are better for outdoor use and large spaces like warehouses. Do you live in the right climate for an evaporative cooler?

Evaporative coolers humidify dry air with a cool mist. There are three main measurements of humidity: relative, absolute, and specific. Absolute humidity (units are grams of water vapor per cubic meter volume of air) is a measure of the actual amount of water vapor in the air, regardless of the air’s temperature.

Relative humidity, expressed as a percent, measures the current absolute humidity relative to the maximum (highest point) for that temperature. Ideal room humidity, as measured by a hygrometer, should be between 20C and 22C (18C for a bedroom) with a relative humidity of 40% to 60%. As with air conditioners, replace the filter according to manufacturer recommendations.


Thermodynamics is the branch of physics concerned with heat and temperature and their relation to energy and work. A descrip­tion of any thermo­dynamic system employs the four laws of thermo­dynamics that form an axiomatic basis.

The first law specifies that energy can be exchanged between physical systems as heat and work. The second law defines the existence of a quantity called entropy, which describes the direction, therm­odynamically, that a system can evolve and quantifies the state of order of a system and that can be used to quantify the useful work that can be extracted from the system.

The study of thermo­dynamical systems has developed into several related branches, each using a different fundamental model as a theoretical or experimental basis, or applying the principles to varying types of systems:

  1. Classical thermo­dynamics
  2. Statistical mechanics
  3. Chemical therm­odynamics
  4. Equilibrium thermo­dynamics

Evaporative coolers tend to work best when relative humidity is 60% or less. However, evaporative coolers can work in humid conditions when they are used in semi-outdoor (loading bays and docks, garages) and outdoor conditions for moisture evaporation. Because of the potential for moisture build-up indoors, an open window or door is required for use and not recommended for indoor use in humid climates.


Usually, fans employ circulating blades. Oscillation is a popular upgrade. Some modern silent fans are bladeless. A light breeze in the room typically gives the feeling of the temperature being cooler than it is.

Fans do not cool the air. They circulate air to speed the evaporation of human sweat on the skin's surface, thereby cooling our bodies. Essentially, they turn our bodies into evaporative coolers. Perceived effectiveness is increased by the rate of perspiration.

Battery-operated handheld fans, USB devices, and desktop evaporative coolers are not designed to drop the temperature of an entire room. They offer convenient personal space comfort up to about 19 inches (half a meter) away from your face. They might be used next to a computer while working. Of course, you need to make certain that they do not blow away any papers off your desk.

When it is warm stay hydrated by drinking plenty of fluids. Water is better than diuretic caffeinated or alcoholic drinks. You can also open multiple windows—ideally on opposite ends of the room—to create a draft should there be any breeze.

This also improves the efficiency of fans as they circulate fresh air. If you are at home, taking a warm shower can bring down your body temperature and remove sticky perspiration. This should make you temporarily feel better.

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