Air Conditioners, Air Coolers & Fans

Dehumidifier Buying Guide

In addition to being uncomfortable, humid indoor air also causes damage to your home and furnishings, and promotes the growth of mold and dust mites. Thankfully, purchasing a quality dehumidifier is the perfect solution to excess household moisture.

Moisture Problems

If you notice creaking floors, condensation developing on windows, or exacerbated allergy symptoms, your home's humidity levels may be out of whack. Low humidity levels can cause problems such as increased static electricity; respiratory problems; and cracking and peeling of furniture and paint, but purchasing an inexpensive humidifier for your home is an easy solution. However, high humidity levels are often a more challenging problem. If your home is too wet, it can be a breeding ground for mildew growth; stained ceilings and walls; and excess condensation on windows and mirrors. Those living in hot, humid climates may also find that their homes provide the optimal environment for pests such as termites. The chart below illustrates how humidity levels can affect your health and home:

Common Symptoms

What is a Dehumidifier?

Dehumidifiers are household appliances that help reduce the humidity levels in the air. There are primarily two types of humidifiers - desiccant and mechanical.
Excess humidity not only causes discomfort, but it can also add to your air conditioner's load. Therefore, a dehumidifier not only keeps you comfortable, but it can also help you save money on your AC bill.



Desiccant dehumidifiers (or passive dehumidifiers) are named for their use of a desiccative substance to dehumidify the air. This substance has an affinity for water vapor, and the dehumidifying process involves exposing the desiccant matter to an air stream with high relative humidity. These dehumidifiers do not utilize compressors and are best used in areas with low temperatures and relatively low humidity levels. Desiccant dehumidifiers can also be used instead of mechanical units or in combination with them. Although not as efficient as mechanical models, they are usually very inexpensive to purchase.

Dessicant Dehumidifier
Dessicant Dehumidifier

Mechanical Dehumidifier
Mechanical Dehumidifier


Mechanical dehumidifiers (or active dehumidifiers), however, are much more common, efficient, and are simply air conditioners with both the hot and cold coils in the same box. A fan draws the room's air over the cold coil of the AC to condense the moisture, and this is often collected into a bucket. Dry air will then pass through the hot coil to heat it back up to its original temperature. Therefore, mechanical dehumidifiers will slightly raise the air temperature, as opposed to air conditioners, which will cool the air as it dehumidifies it.


While very small spaces may only require passive dehumidifiers, rooms or larger areas with moisture problems will require a mechanical dehumidifier that either utilizes compressor or thermoelectric technology. Here are the main differences between the two different types:

Dehumidifiers with Compressors

This is the most common technology utilized by dehumidifiers. Like air conditioners, compressor dehumidifiers have coils through which compressed air or refrigerants move. In other words, one set of coils is cooled by moving heat to the other set of coils. A fan within the unit pulls moist air from the room over the cool coils, and this cools the air and causes water to be condensed and to fall into a collection bucket. Dehumidified air is then passed over the hot coils where it is warmed back to room temperature and passed back into the room. Although these types of dehumidifiers are somewhat loud, they are extremely effective.

Dehumidifiers with Thermo-Electric Peltiers

These types of dehumidifiers utilize thermo-electric technology. An electric current is passed through two dissimilar metals which transfer heat, and this causes the same effect that is used by compression technology. The one benefit to this technology is that there are no moving parts so the only noise that is emitted from these units is produced by the fan that circulates the air. Although less energy efficient than compressor dehumidifiers, they are effective for smaller areas and offer almost silent operation.


When shopping for a dehumidifier, there are several factors to consider such as the size of the unit, dehumidification capacity, and safety features. Below is a list of some of the most common things to look for when choosing a dehumidifier and what they mean to you:


The size of a dehumidifier is generally based on the amount of moisture extracted from the air in 24 hours, which is usually measured in pints. Purchase a larger capacity model over a smaller one because larger units can dehumidify more area in a shorter amount of time. Furthermore, a dehumidifier with a smaller capacity may run continuously and still not lower the humidity to proper levels.


If you're looking to move your dehumidifier from room to room, look for a unit that is compact, lightweight, and includes a carrying handle or rolling casters.

Built-In Humidistat

If you'd like to be able to adjust different humidity levels, finding a dehumidifier with a humidistat is key. This feature will automatically turn the unit on/off depending on the humidity setting.

Automatic Shut-Off

This function will allow you to turn the unit on or off without having to unplug it, and it also prevents overfilling when the storage tank is full.

Low Temperature Operation / Automatic Defrost

If you may be using the dehumidifier in temperatures colder than 20 C, look for a unit that has an anti-frost sensor and can operate in cold temperatures. This prevents quick cycling and frost from accumulating on the sensor.

Storage Tank Capacity

Almost all dehumidifiers have storage tanks for the collected water. If you're not planning to purchase a model with a continuous drainage port, you'll have to empty the tank periodically. If the dehumidifier is to be placed in an area where you may not be able to empty it frequently, look for a tank size of at least 15 pints.

Continuous Drainage

Dehumidifiers with a continuous drainage port will eliminate the hassle of emptying a condensation tank. Simply attach a hose to the dehumidifier, and the moisture will drain out through the hose.

Washable / Removable Air Filter

Dehumidifiers that have washable filters trap airborne dust and particles. If the filter is washable, this makes maintenance a breeze: simply pull out the filter; rinse it with mild soap and water; and replace it back within the unit.

Placement of Dehumidifier

When it comes to dehumidifiers, placement is also important. If the unit has an air vent on top, it can be placed against the wall. If it doesn't, it will need to be placed away from walls and furniture for proper circulation.
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