Most people are familiar with a compressor dehumidifier. It’s been around in our homes for almost 50 years. But did you know that there’s also another type of dehumidifier to consider – the desiccant dehumidifier?
But what is the difference between a compressor dehumidifier and a desiccant dehumidifier? A compressor dehumidifier removes water from the air by running it through refrigerated coils and then capturing it as condensate. It works similarly to an air conditioner. A desiccant, on the other hand, simply adsorbs the moisture from the air by spinning the air through a desiccant wheel.
Both types of dehumidifiers have their pros and cons. Desiccant dehumidifiers are best in areas that are already dry and cold, while compressor dehumidifiers are best during the warmer seasons where moisture levels are already high.
Let’s go into more detail and argue why you may wish to choose a desiccant dehumidifier for your home.
How a Compressor Dehumidifier Works
In the most simplest of terms, a compressor dehumidifier removes moisture by condensing the air below its dew point. It cycles the air inside a home and collects it through refrigerated coils. As the air moves through the coils, it condenses and is collected as water into a bucket or through a hose. The condensate is then ultimately pushed out again by changing it back from a water to gas state with the help of an internal heater.
A compressor dehumidifier, in summary, must have the capacity to cool the air to the point of condensation, as well as to heat it back up so that it can cycle back into the space.
How a Desiccant Dehumidifier Works
A desiccant dehumidifier is more lightweight and quieter than the traditional compressor dehumidifier. It primarily adsorbs the moisture from the air, and then uses a heater.
Its main technology is a desiccant wheel rotor that’s typically coated with a woven honeycomb mesh of some sort of adsorbent like silica gel, for example. This mesh is highly effective thanks to its high surface area. As the wheel spins, it first absorbs moisture from the wet air and then desorbs it back out into the room.
Most of the air that exits is just dried air, known as process air. The rest of the expelled air is heated as it’s released out of the wheel and into the room. This portion of the heated, dry air is known as reactivation air. We’ll go into a bit more detail about this later on in the post.
Many residential desiccant dehumidifiers will still condensate the water vapor and collect it similar to a compressor dehumidifier, although its primary, initial step is the desiccant wheel. Some desiccant dehumidifiers, however, only have a desiccant wheel since the cooling feature is not an absolute must for it to function.
The Benefits (and Limitations) of a Desiccant Dehumidifier
The benefits of a desiccant dehumidifier far outweigh its disadvantages. Let’s go into more detail.
Lower Operating Temperatures
The desiccant dehumidifier is not limited by the surrounding temperature as much as a compressor dehumidifier is.
Compressor dehumidifiers are highly sensitive to the ambient temperature and can sometimes appear to remove moisture inconsistently because of this. They’re great during a hot summer and when the ambient air is already saturated with a lot of moisture (known as high relative humidity, or RH).
But once the temperature starts dropping and the bulk of the humidity has been removed, the compressor dehumidifier begins to struggle.
First, it has a hard time squeezing out the “final” excess moisture from the air. For example, it will be much easier for a compressor dehumidifier to go down from 85% to 75% relative humidity (RH) than it will be to go down from 75% to 65% relative humidity (RH).
Second, it starts struggling once the ambient air temperature gets below 59°F. Compressor dehumidifiers spend the majority of their operational time defrosting its coils and only a small portion actually removing excess moisture. An ambient temperature below 59°F will force the compressor dehumidifier to just try to defrost its coils, leaving very little room for its main purpose – dehumidification.
This can be quite the drain on your energy bill if you let the compressor dehumidifier run at night, or plan to run it in a basement, cold area of your home, or during the fall or winter (check out this post if you want a cost estimate of how much a dehumidifier will add to your energy bill).
What’s even worse is that most people aren’t aware of this until they receive their electricity bill at the end of the month. The coils freeze up and the compressor dehumidifier essentially is only running its fan without removing any excess moisture.
This is why a desiccant dehumidifier is so beneficial. You don’t need to worry about the seasons, ambient temperature, or what the current relative humidity (RH) level is. It runs the same, regardless.
The graphs show its consistency at various temperature and humidity levels.
(Source: EcoSeb user manual)
Lower Energy Costs (Sometimes)
This benefit comes with a caveat, and that is that compressor and desiccant dehumidifiers have their ideal operating environment.
Generally speaking, a compressor dehumidifier uses less energy compared to the same-size capacity desiccant dehumidifier. This is especially true with Energy Star-rated compressor dehumidifiers.
But there are some instances where a desiccant dehumidifier will cost far less on your energy bill (again, I’m talking about reasonably-sized desiccant dehumidifiers here, not small dehumidifiers that may not even use any electricity).
During the late spring, summer, and early fall, a compressor dehumidifier is the best option since the temperature rarely gets to a point where its coils must constantly freeze. But if you’re looking for a dehumidifier during the winter or you live in the cold Northern climates, consider a desiccant dehumidifier.
If you can afford it, it’s best to have both types of dehumidifiers in your home and change them out with the seasons.
Also keep in mind that you run the risk of damaging a compressor dehumidifier beyond the point of repair if you let it operate below 59°F. It’s better to drain and clean it out as it gets colder outside, keeping it tucked away during the winter so that it can last another year.
Great For Your Laundry Room
Many desiccant dehumidifier have a setting known as “laundry mode.”
Turning this on to high simply means that the dehumidifier humidity level is set to around 40% relative humidity, allowing your laundry to dry naturally within just hours thanks to the fast air flow inside a desiccant dehumidifier.
This is something that compressor dehumidifiers are unable to do and a great feature that sets desiccant dehumidifiers apart.
Although, always be mindful that the human body needs at minimum a relative humidity of 35% or higher to function properly. If you feel dry skin, dizziness, or have an itchy throat, it means that the humidity level needs to be set higher.
Most residential compressor dehumidifiers weigh about 25 to 35 pounds and can be clunky to move around. Desiccant dehumidifiers that are able to remove the same amount of moisture in rooms at about 60 to 75°F are more lightweight, typically weighing about 13 to 20 pounds.
Some desiccant dehumidifiers require no electricity whatsoever since they only rely on the desiccant recharging naturally or by battery operation, although you’ll be limited to using them in small bathrooms, laundry rooms, pantries, closets, or similar. Examples of these desiccants are the ProBreeze cordless dehumidifier and the EvaDry line of mini dehumidifiers.
The EcoSeb DD122EA dehumidifier (find its lowest price on Amazon here) has always been my favorite and I’ve recommended it on this blog before. The reason I like it is because its noise level is only 34 decibels (dB), and yet, it’s potent enough to remove 15 pints of water per day.
The larger Ecoseb DD322EA, removes 21 pints of water per day at only a 36 or 42 decibel (dB) noise level, depending on the model chosen.
These desiccant dehumidifiers aren’t the only ones that are this quiet, though. Most desiccant dehumidifiers are quiet by default. Even next to a compressor dehumidifier that’s touted to have “whisper” technology, a desiccant dehumidifier will almost always be the quieter one.
Let’s put this into context.
Most average compressor dehumidifier noise levels are at about 48 to 60 decibels (dB). I’m talking about sizeable dehumidifiers (15 pints and up) for decent-sized rooms, not the small dehumidifiers that can only dehumidify a few dozen square feet of space.
The lower end of that spectrum is where you’ll see compressor dehumidifiers being marketed as having “whisper” technology. In reality, this is somewhat deceiving.
The noise level of actual whispering is at 30 decibels (dB), so most dehumidifiers simply aren’t that quiet, no matter how they’re being marketed. Their noise levels are closer to that of a large stainless steel refrigerator in the kitchen or a conversation in the living room, which is at about 50 decibels (dB).
So if you’re looking for a dehumidifier that runs quietly in the background while you sleep, a desiccant dehumidifier with a noise level between 30 and 45 decibels (dB) is a must. A 30-decibel (dB) level will be comparable to the sound level of whispering and a 40-decibel (dB) level will be comparable to the soothing sound level of nature.
Warmer Air During the Winter
As mentioned, part of the compressor dehumidifier cycle is to warm up the condense water vapor and convert it into gas again. This is achieved by an internal heater. Generally, this warm air is only 2 to 4°F warmer than the initial air temperature in the room.
A desiccant dehumidifier is a bit more complicated.
Remember that I mentioned that desiccant dehumidifiers partly heat some of its expelled air (known as reactivation air)?
Since the adsorption inside the wheel is mostly based on chemical attraction, some of the air must be heated beyond the naturally generated heat to break up these bonds. This essentially pries away any residual moisture and flushes the desiccant wheel, making it ready for the next cycle. This is why it’s called reactivation air. Without it, the desiccant inside the wheel couldn’t be reused for the next air cycle.
Adsorption inevitably is a process that requires and releases a lot of heat. Internal heaters on a desiccant wheel can reach as high as 140°F, so by the time the air is expelled out into the air, the overall surrounding room temperature could be at minimum 10°F warmer than the air temperature in the room. For example, the EcoSeb DD322EA model claims to expel air that’s 44°F warmer.
In short, a desiccant dehumidifier will act as a heater during cold winter months, causing your central heating to turn on less frequently in your home.
Safer Compared to a Compressor Dehumidifier
Older models of compressor dehumidifiers use Freon (R-22) gas for its coils, which can be quite dangerous if there is a Freon leak.
Luckily, this type of gas has been phased out, so most compressor dehumidifiers now have swapped the dangerous R-22 refrigerant for a friendlier R-410A refrigerant. This new refrigerant is said to be eco-friendly since it doesn’t contribute to dangerous ozone creation, plus it boots the additional benefit of using less heat.
Although, it’s still a refrigerant and it can still leak. While it may not have dangerous levels of chlorine like the old R-22 refrigerant did, it still is an irritant.
The real note-worthy risk to a dehumidifier nowadays is its fire hazard. In fact, manufacturers are routinely recalling hundreds of thousands of dehumidifiers on an annual basis due to fire hazards. You can check recent recalls here.
And sadly, these recalls are predominantly for compressor dehumidifiers and less for desiccant dehumidifiers.
It mostly has to do with overheating due to frozen coils, which frequently happens when the auto defrost malfunctions or when the dehumidifier doesn’t have an auto defrost at all.
Desiccant dehumidifiers sound great on the surface, but there are a few limitations.
First, they will significantly warm the air, which mostly comes from the heat that’s released as moisture reacts chemically with the adsorbent molecules. Compressor dehumidifiers also warm the air, but only by a few degrees Fahrenheit.
You can expect the desiccant dehumidifier to warm the air by as much as 10°F to 50°F. Obviously, this is great in the winter, but not in the summer, when there is a bigger need to use dehumidifiers.
A desiccant dehumidifier is best during the winter or in areas where moisture levels are already low, but outside of that, a compressor dehumidifier usually is the better choice.
Compressor dehumidifiers are best for large rooms or areas in your home. These are the typical 30-pint dehumidifiers that are commonly available, or even larger. Make sure the one you choose is Energy Star-rated since dehumidifiers can often take up a large chunk of your energy bill.
Low levels of relative humidity (RH) and low temperatures are where a compressor dehumidifier has its limitations. Make sure to drain it out and tuck it away during a cold winter season and to not force it below a humidity level it can’t reach.
Desiccant dehumidifiers are emerging as an alternative to old-fashioned compressor dehumidifiers. Their water-removal capacities are becoming larger and they’re becoming more accessible and affordable to the average consumer.
Their pros far outweigh their cons. They’re more lightweight, quieter, safer, and are able to go beyond the temperature and relative humidity (RH) limitations of a traditional compressor dehumidifier.
However, compressor dehumidifiers still remain the standard. They’re still more affordable and the Energy Star-rated units use less energy (if used properly and during the right season).
Desiccant dehumidifier technology will need to keep evolving to solve these problems and eventually overtake compressor dehumidifiers in the near future.
Should you run a dehumidifier in the winter?
The US Department of Energy (DOE) recommends that dehumidifiers should run between April and October, with the bulk of the operation during the middle of the summer months. While some of the reasoning makes sense (the summer is when moisture levels are highest, after all), much of that reasoning is based on the dated idea of old, compressor technology.
In short, use a compressor dehumidifier as recommended, but there’s nothing stopping you from also using desiccant dehumidifiers during the cold season to thwart mold and dust.
Mold and dust don’t take a seasonal break, and neither should you with your dehumidifier(s).
Can one dehumidifier do multiple rooms?
It depends, but the answer is more likely to be a yes if you understand how temperature and relative humidity (RH) work.
If you have a large 70-pint or 90-pint dehumidifier in a small- to medium-sized basement, it will definitely help to some extent, as long as you keep all the basement doors open. Take a look at the graph above to understand just how many pints your dehumidifier will need to be able to remove, then read this post to help you make the right choice.
How much will dehumidifiers increase my electricity bill?
It depends, but you can expect your dehumidifier to pretty much be on constantly during the summer months.
Generally speaking, you can expect a dehumidifier to run you at about $15 to $20 a month for each level of your home per month. Here’s a post that breaks down the electricity bill further.