What to Consider When Buying Dehumidifiers

If you’ve started to notice a build-up of mold on the ceiling of your home or in the corners of a room, this could indicate that you need a dehumidifier to help tackle the problem of excess moisture (humidity) in the air.

With this in mind, there are many considerations to bear in mind before you go online and purchase a dehumidifier for your home.

In this article, we’ll discuss a range of factors and questions you might want to ask yourself while researching the best possible dehumidifier for your home:

What are the signs that I need a dehumidifier?

Aside from the unwelcome presence of mold spots, there are a range of telltale signs that your home might need a dehumidifier.

Stuffy smells

Stuff smell in the home

Stuffy smells in the home

One of the most prominent clues that you might need a dehumidifier is if you can detect a musty or mildew smell throughout your home, which is usually caused by the growth of mold or mildew.

This growth is often encouraged by the lack of proper ventilation, which is indeed not good for your health. A dehumidifier or an air purifier specially designed to tackle mold may help in the fight against unwelcome growth.

Excess condensation

Condensation signs in the home

Condensation signs in the home

During the winter months, you might start to notice condensation and water beads on the inside of your windows, which could indicate that the room has too much moisture in the air.

It’s vital that you try and determine where the excess moisture is coming from before you enlist the help of a dehumidifier to get rid of the excess moisture so that you can tackle the issue effectively.

Sudden allergies

Sudden allergies in the home

Sudden allergies in the home

If you find yourself suddenly sneezing or coughing because of allergies, this could be an indication that there is too much mold or bacteria in the home, which could be being encouraged by excessive humidity.

Buying a dehumidifier also helps keep dust mites and indoor air pollution at bay, which can help ease the symptoms of troublesome allergies.

Rotting wood

This won’t be relevant to everyone, but if you have wooden beams in your home, or exposed wood or furniture, the fact that there is rotting is a sure sign that there is too much moisture in the air.

Quickly replace affected wood and check your home to see if there has been a water leak, which can sometimes cause excessive humidity levels.

What kind of dehumidifiers are there?

When on the search for a dehumidifier, it is essential to know what type of dehumidifier you need, as there are two main types, and each one tackles the issue of humidity differently.

Refrigerant dehumidifiers

A refrigerant (compressor) dehumidifier works by drawing in the damp air before passing it over a cold evaporator coil, which operates to condense the moisture out of the air.

Cooled below the air’s dewpoint temperature, the condensation is then collected from the cold coils and water is collected in a pan or tank.

The dry air in the machine is then passed over warm condensing coils, which heat the air before it is released back into the room.

In many machines, the dry air is pushed out at a pressure so that it can be directed at specific areas of a room suffering from damp. It helps enable an accelerated drying process.

Desiccant Dehumidifiers

Desiccant dehumidifiers work by passing air through a rotor that is equipped with moisture absorbent desiccant materials.

Once that water is removed from the air within the machine, dry air is blown back into the room; encouraging the drying process.

Water collected in the desiccant wheel is removed by adding heat so that vaporized moisture can then be removed.

Typically, the desiccant material is a silica gel, which takes the form of granular silica. The internal structure comprises of a network of microscopic interconnected pores, and these absorb the moisture by attracting it within each granule, working a little like a sponge.

Which type of dehumidifier is best for me?

Given that the two kinds of dehumidifiers work in different ways, it is essential to know which one will work best in your home, and there are many factors to consider.

Which dehumidifier works best for a cold room?

Garage for a home

Unheated rooms include garages and basements

Because the two kinds dehumidifiers operate differently, it is vital to consider the temperature of a room so that a dehumidifier can work to the best possible level of efficiency.

If you plan on using a dehumidifier in a room that is less than 15°C (59°F), such as in a garage or a basement, you should consider buying a desiccant humidifier.

It is because the internal workings of a compressor dehumidifier need to be colder than the air within the room in which it is situated.

So a room that is less than 15°C (59°F) will make it difficult for a compressor dehumidifier to do its job.

A compressor dehumidifier working at a room temperature of around 50°F means that the inside of the machine will be operating at temperatures that are close to freezing, which increases the chances of ice forming on the machine’s cooling coils.

Desiccant dehumidifiers can operate in rooms regardless of the overall temperature.

Dehumidifiers for warming rooms

Living room and dining area

Dehumidifiers can help heat rooms in any home

Although not their primary function, many people search for a dehumidifier that can keep their home’s humidity levels at bay while also working to raise the overall temperature.

Both types of the humidifier can warm the air within a room, although this will vary depending on the kind of dehumidifier that you are using.

The air that is released from a compressor dehumidifier will be only slightly warmer than room temperature, while the air that comes out of a desiccant dehumidifier will be around ten degrees warmer, so there is quite a difference between the two.

It’s worth bearing in mind that success in this matter will depend on the size of both the dehumidifier and the room or home that it is operating in.

Are there any differences in extraction efficiency?

If you were to compare two similarly sized dehumidifiers, one being a compressor and the other being a desiccant dehumidifier, you would generally find that a compressor dehumidifier will be able to remove a larger volume of moisture from the air during the same period.

It means that in the unfortunate event of a flood, compressors are particularly useful during restoration processes when saturated environments require rapid drying.

Of course, it’s always recommended that you check the extraction rate of each make and model that you are considering to ensure that it meets your requirements.

Many good quality dehumidifiers are highly efficient, and a modern one may collect the same amount of moisture from the air during a six-hour period than a model from 20 years ago operating for 12 hours.

What are the running costs of dehumidifiers?

Generally, you will find that a compressor dehumidifier consumes less energy than a desiccant dehumidifier, so they are cheaper to run on a whole.

However, each model will come with its energy rating, so this is another crucial factor to consider when purchasing a dehumidifier.

The rating of most dehumidifiers are measured in watts, and it’s important to consider that the wattage figure is often far less than an average electric heater.

On the whole, dehumidifiers are generally cheap to run as they are not required to operate 24 hours per day in a regular home.

Your typical dehumidifier will cost between 6p and 10p per hour, and on an average month, depending on usage, a household can expect costs from £15 to £35 (or £12 to £27) during the summer.

Energy Star Rating

Energy Star

For US residents, we advise looking for the ENERGY STAR® label, which is used on dehumidifiers that save electricity by removing humidity more efficiently. For UK and EU residents, we advise looking for an Energy Label (A-G), which gives information about the energy efficiency of a product.

If you are choosing between two ENERGY STAR models, it is worth looking for the higher energy factor, which considers litres of water removed per kilowatt hour of electricity used (L/kWh).

Find out more with our ‘How Much Does it Cost to Run a Dehumidifier?’ guide.

What size dehumidifier should I look for?

For your typical domestic dehumidifier, you will be able to find them on the market for between 0.5 and 20 litres, which serves as an indication of how much water they can hold.

As you can imagine, the best-sized dehumidifier depends on the space of the environment in which you want to use it.

For example, if you are going to use a dehumidifier in a small room, such as a study or a child’s bedroom, you would be best searching for one that is lower in capacity.

However, if you are looking to use a dehumidifier that serves the entire house, you will want to search for one of the larger models.

One thing that you might notice while searching for a dehumidifier is the difference between a machine’s capacity and that of its water tank capacity.

This is because a dehumidifier’s capacity is the amount of water each model can extract from the air over a 24 hour period, while its water tank capacity is how much liquid it can hold at its maximum limit.

It’s worth bearing in mind that the amount of water an average dehumidifier can extract each day will be more than the amount of water that it can hold in its tank. It means that it will need emptying once or twice a day if you need to use it for an extended period.

Many dehumidifiers will have hose attachments so that water can be drained from the tank so that the machine can extract moisture from the air continuously.

What features should I look for in a dehumidifier?

Each dehumidifier is, of course, different, and there are a range of features that you can look for in each brand and model.

Here are a few of the most common or useful features that you should consider during your search:

Frost watch

If you’re looking to buy a compressor dehumidifier, search for one that has “frost watch”, which means that it contains technology that will prevent water from freezing on its coils when being pulled from the air.

Desiccant dehumidifiers tend not to have this technology installed.


Ecoair humidistat

Ecoair humidistat

A dehumidifier with a humidistat can monitor the moisture in the air so that it can turn itself off to maintain the humidity level that has been selected by the user.

This means that you don’t have to repeatedly turn the machine on and off by hand when the room reaches the desired humidity.

Some dehumidifiers also come with timers so that you can choose how long a machine operates.

Continuous drain facility

This is perfect if you need to be elsewhere while the dehumidifier is in operation.

The feature allows you to connect a hose so that the water is continuously directed away to a low-level drain.

When buying a dehumidifier with a continuous drain facility, check whether it comes with a hose, as sometimes these will need to be purchased separately at a small cost.

What should I consider before using a dehumidifier?

Just like any other piece of machinery that you buy, there are also considerations to bear in mind before you use a dehumidifier to ensure both its efficiency and its overall longevity.

The first thing that you should remember is that dehumidifiers rely on an unobstructed airflow to maximise their ability to extract moisture from the air.

Many have vents on the back of the casing, so ensure that there are at least six inches between the end of a dehumidifier and a wall.

Just like a hoover, you’ll also need to clean the filter so that it doesn’t get clogged. Otherwise, you’ll lose out on efficiency, and this could push running costs up.

Check the manufacturer’s instructions on how to safely clean and maintain a dehumidifier.

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