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BUYER GUIDE: Dehumidifiers

BUYER GUIDE: Dehumidifiers

Last edited: 7th September 2023

If you’re thinking of buying a dehumidifier, but have realised there is a lot more choice than you originally expected, you’ve come to the right place. We’ve put together a guide to help you purchase the perfect product for you and your desired use.

What does a dehumidifier do?

Put simply, the purpose of a dehumidifier is to remove excess humidity from the air. How they operate is not quite so simple, as there are a few different options to choose from:

  • Compressor
  • Desiccant
  • Peltier

The Peltier option is the least likely option you will find available, for numerous reasons.

Peltier technology dehumidifiers generally have a low operating range and lower efficiency than compressor or desiccant options, generally only producing approximately 0.1 to 0.2 lt in a 24 hour period.

Because of these reasons, this guide will be focused upon the more popular alternative options of compressor and desiccant dehumidifiers.

Why would you need a dehumidifier?

  • Are you suffering from damp in your property?
  • Have you noticed unsightly mould appearing in your property?
  • Are you concerned about dust, bacteria and germs?
  • Have you experienced a ‘musty’ smell or noticed cold areas in the property?

All of the reasons above (plus many more) are good reasons to consider purchasing a dehumidifier. But, before purchasing a new unit, it may be worth investigating if any of the issues you are experiencing are being caused by other issues at the property. As good as modern dehumidifiers are, they cannot combat permanent property issues and these should always be rectified first.

If you’re lucky and don’t have any issues within the property, then read on to find out how a new dehumidifier could assist with curing your issues (and maybe even save you money).

By using a dehumidifier on a regular basis, you can help yourself to ensure your property stays mould free or help to cure a mould issue if you have one already. If you have experienced a ‘musty’ smell, this will likely be caused by mould also, so you should notice this to dissipate as the mould dies off.

Dehumidifiers generally have a filter to remove dust spores and unwanted particles from the air, aiding to circulate cleaner air and maintain a fresher feel and smell within the property.

If you dry laundry inside your property, dehumidifiers will remove the moisture from the air surrounding the  laundered clothing, that would otherwise be circulating in the property aiding to the causes of damp and/or stale air.

How does a Dehumidifier work?

Of the remaining 2 types; Compressor and Desiccant, both devices will remove excess moisture from the air and the water that’s removed will be deposited in a ‘water tank’ to be emptied later. Some devices actually have pumps built in, so they can in essence, drain themselves, eliminating the possibility of forgetting to do so yourself.

Desiccant Dehumidifiers

Desiccant dehumidifiers are usually better suited to larger/industrial or Commercial applications.

They work by bringing the colder, damp air into the unit and passing it through a desiccant chemical to absorb the moisture. The desiccant is often placed on a wheel, which absorbs the water from intake air, then rotates and passes a heat source to dry the wheel, where the water is released into a container to be removed later. It also heats the air that has passed through the wheel and recycles it back into the room as warmer, drier air, reducing the relative humidity in the area.

Compressor Dehumidifiers

By far the most common and popular choice for the domestic market place!
Like all mechanical products, these have gone through numerous improvements over the years, but now they have also been developed to operate perfectly in the UK climate.

Unlike lots of parts of the world, the UK climate is mostly a colder and wetter climate, which means we need products that can deal with the conditions that we live in.

When used in ‘normal’ conditions (i.e. no water leaks or issues causing excessive damp) a compressor dehumidifier will be about 50% more economical in operation than a desiccant dehumidifier, for the same volume of water removed from the air!

A compressor dehumidifier operates by using an internal fan, pulling the air from the room into the machine and passing the air over refrigerated coils. This causes the moisture in the air to form into condensation and drip away into a ‘water tank’ at the bottom of the unit, to be removed and poured away later. The air is then pushed back out of the device and comes out as warmer, drier air.

Compressor dehumidifiers work best at operating temperatures ranging from 10°c to 22°c.


Like all technology devices, there are numerous features to look out for when it comes to purchasing the right device for your needs.


Often adjustable (not always adjustable enough) and can allow you to set the desired humidity for the room to be maintained to. Incorrect settings may cause the device to stay on longer than required (using energy and costing money) or not to stay on long enough to achieve the desired effect.

Cheaper products often use cheaper sensors, causing quality issues with this feature.

Daily Water Extraction Rate

Most dehumidifiers are sized by their Rate of Daily Extract (RoDE) and this is measured in Litres (Lt).

Ensuring you purchase a device with the correct RoDE is crucial to achieve the desired result. The size of the property the device will be used in is a good way to sizing the unit.

For reference, you can use the table below (although you should always check the manufacturer’s guidelines):

Number OF Bedrooms

Rate of Daily Extract (RoDE)(Lt)

1 to 2

12 or lower

2 to 3


3 to 4


4 to 5

20 or higher

Water Tank

The moisture that has been removed from the air will be collected into a tank on the unit. The smaller the water tank, the more often the tank will require emptying. When the tank is full, most units will have an auto-stop function, so that the water doesn’t over flow. While this feature is helpful to stop leaks, if you have left the device unattended, it may be off for long periods when you require it to be on and doing its job.

Make sure you get a dehumidifier with a water tank large enough for your requirements or one that also has the option to be continuously drained.

Laundry Function

Designed to aid in removing excess moisture from the air surrounding wet laundry and will also help to dry your laundry quicker.

Defrost Function

When using your dehumidifier during the colder months of the year, it’s possible that the unit may freeze over internally, as the inside components go below freezing point.

Having a device with a defrost function will stop this from happening and keep your unit operating as desired.

Now that you know why you may need a dehumidifier, how a dehumidifier operates, the differences between the different kinds of system operation and the extra functions available, why not browse through the options available?

Of course, if you still need assistance in choosing the right product, our expert advisors are always available to help.