Dehumidifier Buying Guide

A home with too much moisture in the air can lead to a variety of problems. The first is that air that is high in relative humidity can be a breeding ground for things like mildew, mold or dust mites. For people that suffer from respiratory conditions, this can make the home environment almost unbearable. Along with having an effect on home comfort, moist air can also cause physical damage to the home itself and objects like furniture. The best way to address this issue is through the use of a home dehumidifier. However, finding the right dehumidifier for the individual can be difficult.

Dehumidifiers come in a variety of different sizes and designs and they come with a range of different features. In this guide, we will explain some of the different options that the consumer has when it comes to selecting a dehumidifier. Once you have an understanding of the different types of machines that are out there and what they have to offer, you should be better equipped to select the model that will provide the best solution for your home.

Types of Dehumidifiers

On the modern market, there a few different types of dehumidifiers. For this guide, we are going to focus on the two most common designs that are available; those are compressor dehumidifiers and desiccant dehumidifiers. Both of these options can provide an effective solution for removing excess moisture from the air, but they both work differently and they both have their own benefits and disadvantages.

Compressor Models

A compressor driven model uses a refrigerant system that is similar to that of a refrigerator or an air conditioner. The machine uses a fan to pull the damp air into the machine and the set of coils will be used to cool the air as it passes through. As the coils cool the air, the water in the air will condense and drip into a collection pan. These models tend to be better for homes where the moisture problem is connected to the warmer times of year. Many of these machines will have anti-frost systems to allow them to work in colder weather, but the coils can freeze and this causes them to be less efficient and less effective as the temperature drops.

Desiccant Models

A desiccant model works in a way that is very different from the models that use a refrigerant system. With these models, the air is drawn through the machine using a fan, but instead of using a cold coil to condense the water, the machine will have a desiccant disc to absorb the moisture. The rotor absorbs the moisture and a small heater causes the water to discharge from the disc. The fact that these machines are not dependent on condensation means that they work much better in cold temperatures.

Extraction Level

When you are looking to purchase a dehumidifier, the amount of water extraction that the machine offers will be an important factor. The extraction rate is represented in litres per day and it is based on how much water the machine can extract from the air under its optimal working conditions. If you have a significant problem with damp air, then you are going to want a machine that can extract more moisture per day. While we are not actually talking about the physical size of the machine itself, we break dehumidifiers up into categories like small, medium, large and commercial to reflect their extraction capabilities.

  • Small – Less than 10L of extraction per day
  • Medium – 10-19 litres of extraction per day
  • Large – 20-29 litres of extraction
  • Commercial – 30L of extraction and above

The Humidistat

The humidistat is similar to the thermostat on a heater. It detects the level of moisture in the air and it makes adjustments to the operation of the machine to maintain the proper humidity level. This is a standard feature on just about every model on the current market. Generally, the humidistat will test the air as it goes through the machine and when the correct level of humidity is reached, it will cycle the machine off. Then, when it detects a rise in the humidity, the humidistat will restart the dehumidifier to help maintain the desired level. This is why some models have a fan that continuously runs even when the dehumidifier is not running; it needs to keep air flowing through the system in order to monitor the humidity.

Water Collection

As a dehumidifier removes moisture from the air, it will need some place to send the water. Most machines come with a tank where the water can collect and then the user can empty the container when it is full. An additional option that most machines come with is continuous draining. Depending on your circumstances, either option can work well, but there are a few things to consider.

Tank Size

If you are planning to use the collection tank, then the size of the tank will be an important consideration. A tank that is too small for the unit will be inconvenient because it will require frequent emptying. Generally, you want a tank that is suitable for the level of extraction that the machine provides. For most of the small or medium sized machines, a collection tank of 2.5L or more should be suitable and for the large machines, you probably want to look for a water collection capacity of at least 3L. However, a larger tank is better because it means that you will have to empty the machine less.

Continuous Draining

Most of the dehumidifiers on the current market will also offer continuous draining. The machine will have a place where a hose can be connected to the water tank and the user can run the line to a drain where the water can constantly drain. This is a nice option because the user never has to worry about emptying the machine. Some machines come with all of the pieces that you need for the direct drainage assembly, but there are a few models where you may need to buy a length of hose at the hardware store.

Full Indicator and Auto Stop

When a consumer decides to use the collection tank on the unit, they will want to consider features like whether it has an indicator for when the tank is full and if the machine automatically stops when the tank is full. These are pretty standard features on almost every machine and it would probably be more difficult to find models that don’t offer these features.

However, you do want to make sure that these features work well. If there is a problem with the auto stop feature, then the tank could overflow. With the full indicator, you also want a model that is going to make it clear that the tank needs to be emptied. The machine will not resume operation until the tank is emptied and returned to its position. The sooner that you are aware of the full tank, the sooner that you can empty it and get the machine running again.

Air Filters

A dehumidifier is a machine that processes the air in the environment, so the type of filtration that the machine has can be important. Every model will come with at least some basic level of filtration to prevent damage that can be caused by dirt and dust. However, if airborne particulates and allergens are a particular concern, then you may want to look for a model that offers some level of antimicrobial protection.

The consumer should also consider filter maintenance. The user will need to occasionally clean the filter when the machine is in regular use. A failure to clean the filter will reduce the efficiency and effectiveness of the dehumidifier and it can even impact the operating life of the unit. Most filters will need to be cleaned every 2-4 weeks depending on the conditions of the environment and some may need to be replaced after a few years.

Operating Conditions

The conditions under which the machine will operate will make a difference when you are deciding which dehumidifier will work best. Different models and designs will work better under different conditions, so you want to look for a machine that will provide the optimal performance for the conditions that it is going to be working under. The two primary environmental conditions to consider when you are selecting a dehumidifier are the level of dampness in the area and the temperature.


Humidity problems can range from homes that have the occasional issue with mild dampness to homes where you actually see the water condensation build-up on objects. For homes where the problem is light, you might be able to go with a smaller unit that offers a lower level of extraction. If the home has a significant problem with moisture build-up, then you want to look for a machine that will extract more water per day. Even if the problem is light, you can go with a larger machine because the humidistat will manage the operation to maintain the selected humidity level, but you could save yourself some money by going with a smaller machine.


The temperature in the environment will also make a significant difference to the performance of the machine. Every model has a temperature range at which it will work and they all have an optimal temperature for providing the most efficient and effective performance.

With compressor models, the operating range tends to be from around 5-35 degrees, with the optimal range usually being somewhere between 25-30 degrees. Since these machines rely on a refrigerant system to cool the air, both efficiency and effectiveness will diminish as the temperature decreases below the optimal level. A compressor dehumidifier will be a poor solution for any environment where it is going to have to operate at less than 15-degrees on a regular basis. Compressor models lose their efficiency in cold environments because they have to work harder to provide the same level of extraction and they will have to cycle on and off to allow the coils to defrost.

A desiccant dehumidifier will provide the best performance for environments that are especially cold. They generally have an operating range of around 1-35 degrees and while the optimal range is probably below 20-degrees, there is not a significant loss of effectiveness as the temperature increases. However, desiccant models tend to consume more energy when they are in operation. For this reason, you are better off going with a compressor model in warmer environments.


Additional Features

Controls – The design of the control panel can make a significant difference in regard to the versatility and effectiveness of the machine. The two most common types of controls that are available are electronic and rotary dial. You also want to consider whether the controls allow you to set a specific humidity level or if the machine only offers settings like low, medium and high.

Auto-restart – The auto-restart feature means that the machine will automatically resume operation after a power outage. If you are away and the power goes out, this ensures that it will continue to maintain the desired setting once the power comes back.

Laundry Drying – Reducing the humidity in the environment will always help laundry to dry faster, but there are some machines that have a special laundry mode that goes beyond the drying capabilities of the regular settings. For the best results with these settings, the user will need to put the laundry and the machine in a room with all of the windows and doors closed.

Timer – Having a timer is not an absolute necessity with a dehumidifier, but some people may want to be able to leave the machine running for a predetermined period of time and know that it is going to turn off when they need it to.

Fan Speeds – Every dehumidifier is going to have a fan, but there are a lot of models that only have one operating speed for the fan. The ability to select a fan speed increases the adjustability of the machine and it can be nice to turn the fan down to a lower setting if the noise on the highest setting is excessive.

Portability – If you buy a dehumidifier that you intend to use in different locations, then you want to consider how easy it is to move the machine from one place to the next. Consider the size and weight of the unit and look to see whether it has wheels or a carrying handle.