Dehumidifiers Buying Guide

Dehumidifiers Buying Guide

Posted by Alex Wells on

To perform at our best, we must have a healthy level of moisture in our homes and conservatories. But too much moisture can be detrimental to our heath. This also applies to where we work such as in offices and garages, and where we spend our leisure time such as in caravans and boats.

Woman enjoying her dehumidifed air

What will high moisture levels do?

Excessive moisture in the air can cause damp areas to form on walls and condensation on windows. If this continues, walls, furniture and clothes could be damaged. Eventually, harmful mould could begin to form.

If moisture levels rise beyond 60%, dust mites and bacteria can thrive and breed. This can cause respiratory allergies such as asthma.

Black mould caused by high humidity

What does a Dehumidifier do?

A suitable dehumidifier will not only reduce the build-up of moisture in a room, but can also purify the air around you using filters, creating a comfortable and safe environment.

It does this by removing the excess moisture within a room, helping to maintain a healthy humidity level of 40% – 50%. Additionally, a Dehumidifier can dry clothes on a horse with Laundry Mode switched on.

When looking for the right dehumidifier, it is important to consider the size of the environment. The larger the environment, the larger the dehumidifier needed.

Even in well ventilated areas, a dehumidifier can eliminate moisture build up, for instance in the bathroom caused by hot running water, in the kitchen from a boiling kettle and saucepans, or perhaps in the conservatory from drying laundry and indoor plants.

Devola dehumidifer next to a stylish navy blue sofa

How does a Dehumidifier work?

A dehumidifier does 3 things:

  1. It draws in the moisture from the air
  2. It collects the moisture in a water tank
  3. It re-releases purified air back into the room

There are two main types of dehumidifiers, Compressor Dehumidifiers and Desiccant Dehumidifiers.

Graph showing the effectiveness of differrent types of humidifiers

Compressor Dehumidifier:

Compressor dehumidifier example

  • The moist air is drawn over a filter by a fan which cleans the air
  • The air then passes over a set of cold coils
  • The coils are made cold by refrigerant coming from the compressor
  • The air is reheated by a warm set of coils
  • The regulated dry air is then released back into the room
  • The excess moisture is collected in the unit’s internal water tank or drained via a continuous drainage system

Compressor dehumidifiers also have either a HEPA or Anti-Bacterial Filter to remove dust and allergens from the air before it is released back out.

Desiccant Dehumidifier:

Diagram showing how a desiccant dehumidifier works

  • The moist air is drawn over a filter by a fan which cleans the air
  • The air hits a rotating wheel full of desiccant Zeolite material
  • The desiccant absorbs moisture from the air
  • The wheel rotates and the excess moisture is removed by a small fan and heater
  • The warm, damp air passes through a condenser
  • The moisture is collected in the internal water tank or drained via a continuous drainage system
  • The heat is delivered to the room with the dry air
  • The regulated air is 10-12°C warmer than the room
  • temperature

Desiccant dehumidifiers are on average quieter and lighter than Compressor dehumidifiers because they do not need a Compressor.

Compressor v. Desiccant

 Compressor Desiccant
Pros: Pros:
  • The most common type of dehumidifier used in the home and bedroom 
  • Lower running costs 
  • Collects higher volume of moisture in warm and humid conditions 
  • Higher capacity than equivalent desiccant dehumidifiers 
  • Additional HEPA or anti-bacterial filters 
  • Operates effectively in conservatories, garages, boats, and caravans 
  • Work efficiently in colder environments with temperatures below 10°C
  • Lighter models than compressor which makes them portable 
  • Usually quieter models than compressors 
  • More consistent performance than compressors 
Cons: Cons:
  • Poor performance in environments below 15°C
  • Noisier models than desiccants 
  • Heavier models than desiccants which makes them less portable 
  • When used in roome below 16°C the defrost programme causes the internal coils to freeze over
  • Less energy efficient than compressors 
  • Do not work in high temperatures above 22°C
  • Poor performance above room temperature 
  • Higher running costs than compressors 


What is the most suitable Dehumidifier for my environment?

 Living Room

Modern living room

Compressors are ideal for living rooms where the refrigerant will work effectively at room temperature.

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Large garage

Desiccants work best for garages. They can overcome the condensation and damp, and can heat up the air temperature by 12°C.

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Modern bedroom

Compressors work well in the bedroom given the higher room temperature.

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Stylish caravan

Desiccants are ideal for caravans given their compact size and ability to operate in colder temperatures.

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Modern houseboat

Desiccants are perfect for boats and can be left on their own to work effectively. The dehumidifiers switch off on their own once target humidity has been reached.

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Stylish walled conservatory

Desiccants are perfects for conservatories as they work most efficiently below 15°C. They can be left on their own and will automatically switch off once they reach target humidity.

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Other Things to Consider

Where to Place your Dehumidifier?
Your first consideration is where to place the dehumidifier in a particular environment.

Scenario 1: Large house / Many rooms

To effectively remove moisture from the air in many rooms, it is best to place your dehumidifier in a central area, such as a landing or hallway. Keep all your internal doors open, and the excess moisture will travel towards the dehumidifier. If you have a damp problem in a specific area, place your dehumidifier near that area for a couple of weeks before moving it back to the central area.

Scenario 2: Flooded areas or Burst pipes

In this second scenario, a Building Dryer Dehumidifier will be needed. Building Dryer Dehumidifiers will dry damp buildings quickly and effectively. They can also be used to dehumidify the air after building work, plastering, or decorating.

Features & Benefits of Dehumidifiers

Daily Extraction Rate (L) - How much water the dehumidifier can extract in 24 hours. The more litres a unit has, the higher its extraction rate.

Tank Capacity (L) - This refers to how much water the internal tank can hold in the dehumidifier once it has been extracted from the air. The larger the tank size, the less it needs to be emptied. However, a continuous drainage system will continuously drain the water, saving you the time of emptying the tank.

Power Output (W) - This is how much power the unit uses. This will also help you to work out the running costs.

Noise Level (dB) - How loud the dehumidifier is. An important consideration is where you place the unit, and if noise will be a problem. For example, it is not ideal to place a dehumidifier with a high noise level in the living room. However, this would not be an issue if it were placed in the garage.

Automatic Shut Off - This is when the unit senses the internal water tank is in danger of overflowing, and automatically shuts off. Many dehumidifiers have indicator lights to show when the tank is nearly full.

Automatic Restart Function - This is when the unit automatically restarts when the power goes off. This is helpful if the dehumidifier is left alone for long periods of time.

Laundry Mode - This is an additional feature which allows clothes to dry efficiently. In a lot of scenarios, a dehumidifier with laundry mode is cheaper than a tumble dryer to dry your clothes, as you do not need an open window to let out excess heat. Laundry mode increases the fan speed, allowing the air to become drier.

Defrost Technology - During winter months, a dehumidifier may be working below freezing point, which causes collected water in the tank to freeze. In this scenario, the Defrost function automatically defrosts the unit so that it continues to work normally. It also checks to ensure the mechanism is not freezing, so that the components will not break if the water does freeze.

Ioniser - An ioniser purifies the air. Ions attach to dust particles, making them heavy and causing them to fall to the ground. The dust particles can then be hoovered or wiped away.

Air Filtration - Dehumidifiers can come with either a Dust, Anti-Bacterial or HEPA Filter to purify the air. The Dust Filter will purify the air by drawing in the dust particles. A HEPA (High Efficiency Particulate Air) Filter will purify the air by collecting dust, pollen, spores, bacteria, and various other particles. The filters need to be cleaned regularly and changed once they are worn down. We recommend you change the HEPA Filter once every six months.

Carry Handles and Wheels - Increases portability and makes it easier to transport the dehumidifier. This is especially helpful on Compressor dehumidifiers, as they tend to be heavier than Desiccant dehumidifiers.

Frequently Asked Questions

Q. How much noise will my dehumidifier make?

A. Our dehumidifiers operate at a noise level of 36 – 48 dB. For context, most dishwashers operate around 46-60 dB, so they are quieter than a dishwasher.

Q. Will I be able to sleep at night if I leave my dehumidifier on?

A. Yes, you should be able to comfortably sleep with a dehumidifier running in the same room, unless you are a very light sleeper.

Q. Can the dehumidifier switch off automatically by itself?

A. A dehumidifier will automatically shut itself off if it has an Auto Shut Off function. It will switch off once the target humidity level has been reached. Once the humidity level rises again, the unit will restart to dehumidify your room.

Q. What setting should my dehumidifier be on?

A. We recommend setting your dehumidifier to reach a target humidity of 50 - 55%rh. If you set the dehumidifier any lower it can cause the air to become too dry. However, if you are using the dehumidifier to dry your washing or a room following a leak, we recommend setting it to Cooling Mode or Laundry Mode.

Q. Why have I not received my filter?

A. The filter is connected to the filter case. It is very thin and can be hard to see. If you cannot put your fingers through the filter case, it means the filter is there. It is extremely unlikely that a filter would not be provided with the dehumidifier.

Q. What is an ioniser?

A. An ioniser releases ion into the air. These ions attach to dust particles making them heavy so that they fall to the ground - this means they can be hoovered or wiped away.

Q. Which dehumidifiers have castor wheels?

A. The majority of our dehumidifiers come with castor wheels. Castor wheels make it easier to carry your dehumidifier to your bedroom. These dehumidifiers come with castor wheels.

Q. Which dehumidifiers use HEPA filters?

A. HEPA (High Efficiency Particulate Air) filters remove dust, pollen and other particles from the air, purifying the air quality in the room. These dehumidifiers all have HEPA filters.

Q. Why do you not supply a drainage hose?

A. We removed hoses from our dehumidifiers as 90% of our customers did not require one. This small change has prevented 70,000m of plastic entering landfill each year.

Q. Why is my dehumidifier still running after reaching its target?

A. Once the dehumidifier has reached its target it will continue to run until the humidity level has stabilised. This could be a couple of minutes or even a couple of hours. If you would like your dehumidifier to stop running, increase the target slightly.