How Do Peltier Dehumidifiers Work?

Dehumidifiers come in a wide variety of sizes. Some of the most compact and portable models use a method of dehumidification based on the Peltier Effect or thermoelectric cooling, thus called Peltier or thermoelectric dehumidifiers. The main difference from the more common compressor models is their size and coverage. Peltier dehumidifiers are particularly popular for their quiet operation and inexpensive price. So, if you need a dehumidifier for a small room with minimal moisture, then you may want to know about this type.

Pro Breeze PB-02-US Bedroom Dehumidifier

How A Peltier Dehumidifier Works

The Peltier Effect

It is named after French physicist Jean Charles Athanase Peltier who discovered that a voltage of electricity can be converted to a temperature difference. Prior to this discovery, it had been known that the converse of this was true—that a difference in temperature can be converted to electricity.

The thermoelectric cooling technology involved in Peltier dehumidifiers is based on the Peltier effect. Electricity runs through the Peltier module which creates a temperature difference between its two sides. One side of the module is hot while the other side of the module is cool. This difference in temperature leads to moisture removal from the air.

Dehumidifier Parts

Most Peltier dehumidifiers have a very basic design. They are mainly composed of a Peltier module with two heat sinks, and a fan which facilitates air movement. The fan draws the air into the intake on the front of the unit and out through the exhaust commonly found on the top. 

The cold side heat sink is located where the air enters and moisture is removed. Below is a tank that catches the water collected. It’s usually big enough to hold at least two days worth of dehumidification. The hot side heat sink is on the back where the air passes through before coming out of the exhaust.

A majority of thermoelectric dehumidifiers feature simple controls with a single button for the on/off power switch. Other larger models may also come with a humidistat to adjust the humidity to the user’s desire, or more controls for the fan speed or operation mode.

The Process

How a Peltier dehumidifier works chart

Humid air is drawn by a small fan on one end of the unit and enters through the other, colder front side. As the air cools, the moisture condenses and drips down to the water tank. The cool and dry air then passes through the hot side. Warmer, dryer air exits through the exhaust.

This process is not that different from that of a refrigerant-based dehumidifier, but instead of using a compressor to cool down the coils and remove moisture from the air, a Peltier dehumidifier converts the electricity into a temperature gradient between two sides of the module. As is the case with compressor dehumidifiers, the efficiency also decreases in cooler temperatures.

Advantages of Using a Peltier Dehumidifier

Peltier dehumidifiers can come with a capacity as small as 250ml per day. They are incredibly light and compact. Weighing just a little over 2 lbs, the tiniest models are about 20 times smaller than the typical residential dehumidifier. Due to the size, they are suitable for small spaces and less severe moisture problems. They work very well in smaller areas such as a bedroom, bathroom, laundry room, and even boats or RVs.

Quiet Operation

Perhaps the most attractive feature of Peltier dehumidifiers is the whisper-quiet operation. This is a real advantage over compressor-based and even desiccant dehumidifiers. The only part which produces noise in this type of dehumidifier is the fan, whose sound is usually more pleasant. Compressors produce a buzzing noise when operating, while the fans on both the compressor and desiccant types are much larger than the small 12-volt fans used in thermoelectric dehumidifiers. They can produce as low as 30 to 40 decibels on operation. Because of this, they are ideal for living or sleeping areas where you need a quiet dehumidifier.

Ease of Use

A Peltier dehumidifier generally has a very basic design and few parts that can break. Almost anyone can operate this dehumidifier. There are only a couple buttons (most units even have just one button) with a simple design and label. There is no control panel or digital display you will have to decipher. One push of the button and the unit will start dehumidifying. It will only stop automatically when the tank is full or if you manually shut it off.

When the tank is full, the FULL indicator light will illuminate until you remove the tank and empty the water by hand. The tank can be found on the bottom part of the unit. Simply slide out the tank from the front or back (or one side for some units), remove the lid or plug, and pour the water into the sink or drain. This is all the maintenance you’ll need to do for your dehumidifier.

Energy Efficiency

Electric cost is often a concern for homeowners when using a dehumidifier. Well, a Peltier dehumidifier consumes very little power, as low as 20 Watts for the smallest units. As long as you use it in the recommended area, you’ll feel a significant change in the relative humidity and barely notice it in your electricity bills. At 22 Watts power draw, your dehumidifier will only consume a total of 0.5 kilowatts after 24 hours of use. 

Disadvantages of Using a Peltier Dehumidifier

Peltier dehumidifiers are great if they’re used in the correct type and size of space. But they are also very limited in terms of capacity and coverage.

Moisture Removal Rate

As mentioned, thermoelectric dehumidifiers have very small capacity, typically ranging from 250 ml to one liter per day (or around 0.5 to 2 pints). A full-size desiccant desiccant dehumidifier has a rate of 10 to 20 pints per day, while the most common compressor-bases dehumidifiers for homes can remove 35 to 50 pints of moisture per day. This definitely limits the applications for a Peltier dehumidifier.

Area of Coverage

Because of their small physical size and moisture removal capacity, Peltier dehumidifiers can only be used in very small spaces. They are not a replacement for the bigger and more expensive compressor or desiccant dehumidifiers. They will make little to no change on humidity levels in a large room. Even the bigger units like the Eva-Dry EDV-2200 may not be enough for an average-sized bedroom. 

Take note that most models indicate the recommended coverage area in cubic feet, instead of the more common square footage in other dehumidifiers. This means you need to measure the height, width, and length of the room, and multiply everything. So, if your ceiling is 10 feet high, then 2200 cubic feet can only cover a 220 square feet room. That’s why, the most common Peltier dehumidifiers are only ideal for the smallest bedrooms and bathrooms or other small and enclosed spaces.

Build Quality

Peltier dehumidifiers are inexpensive because they are made with inexpensive and often low quality components. Peltier modules typically last very long, but those that are used in dehumidifiers are cheap and of low quality. The small fan is usually the first to break. However, it can easily be replaced with a basic 12-volt fan used for computers.

This can both be an advantage and disadvantage for the thermoelectric dehumidifier. On the one hand, it’s cheap, small, and easy to operate. But on the other hand, it has a lower quality construction and cheap parts. But then again, replacement parts are easy to find in the rare case that any of them break. So really, it’s up to you and how often or how long you’ll use the dehumidifier.

Value

If you want the best value for your money in terms of the amount of moisture your dehumidifier can remove, then a Peltier dehumidifier may not be the right investment for you. The typical Peltier type is around ten times cheaper than the average 50-pint compressor dehumidifier. Meanwhile, the former has a capacity of about 0.5 pint, which is a hundred times smaller than 50 pints. Obviously, you’ll get a higher moisture removal rate per dollar invested in a compressor dehumidifier. 

However, operating costs are a different conversation. While the same Peltier dehumidifier draws around 20 to 25 Watts, the 50-pint will consume 500 to 700 Watts per hour of operation. If you have a very small space, then a full-size compressor model may be a bit overkill, and not to mention, wasteful of energy. And so, again, it’s up to your own judgment if the Peltier is the right one for you.

Consumer Reviews

Peltier dehumidifiers are popular among RVers for their tiny size and easy, quiet operation. They’re also common in bathrooms and small bedrooms. While there are mostly positive reviews, a lot of the criticisms root from the consumer’s unrealistic expectations. 

Keep in mind that thermoelectric dehumidifiers are specifically designed for very small spaces. Manufacturers specify this on the product description. You cannot expect it to work in the same capacity as a compressor dehumidifier. Opting for the smaller Peltier type just to save some money now will actually cost you a lot more in the long run.

It’s important that you know exactly what you need before you make a purchase. How big (or small) is your space? How much moisture do you need to get rid of? These are only some of the factors you must consider when choosing a dehumidifier. If you need help finding the right model for a specific room or application, we have these guides for you.