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What does a dehumidifier do and is it worth it?

For damp musty homes, this appliance could be your saving grace.

woman emptying water dehumidifier lead
Last updated: 01 June 2021

Need to know

  • Dehumidifiers are a good option if you have persistent damp problems
  • They can be beneficial when drying laundry indoors, as they help reduce condensation and the likelihood of mould developing
  • Consider noise, size and weight to help you choose the right model for the right room

Humidity in your home is a Goldilocks situation. 

Too little, and dry skin and irritated airways might be on the cards. Too much, and your home could be a breeding ground for mould and dust mites, which can trigger asthma and other health problems. 

And, if your home is rife with condensation, it can eventually lead to flaking paintwork and damage to your property. 

If the humidity in your home tends to the high side, it's important to take steps to achieve the right levels. To help you find that 'just right' balance, here's everything you need to know about dehumidifiers.

woman in mouldy room with dehumidifier

Not any spore: A dehumidifier can help prevent the build up of mould in your home.

What does a dehumidifier do?

A dehumidifier removes moisture from the air, helping prevent mould. They mostly work by drawing air in, then filtering and cooling it to condense moisture. It's then reheated before warmer and dryer air is released. 

"Dehumidifiers are a good option if you have persistent humidity or dampness problems," says Chris Barnes, product category manager household at CHOICE. "They're also useful when renovations to improve airflow aren't possible." 

Are dehumidifiers worth it?

Yes, if you've got damp problems. Broadly speaking, cheaper models have fewer features, a smaller tank capacity and may not be as efficient at water removal. Pricier models typically have a better water-removal capability, higher energy efficiency, more features and a larger tank capacity. That said, they'll usually be larger, heavier and often noisier.

They can make a big difference to a persistently damp home

"Dehumidifiers can be expensive to buy, and noisy to run," says Chris. "They'll also add to your electricity bill, as they can use a fair bit of power, which will add up if you have to run them for long periods of time."

In summary? It largely depends on how big your property is, how big your damp problem is… and how big your budget is. 

"They can make a big difference to a persistently damp home and may save you from costly repairs or health problems in the long run," concludes Chris.

Do I need one?

It depends on your home's humidity levels. The National Asthma Council Australia advises they should be between 30 and 50 percent, so a hygrometer – which measures relative humidity – is worth buying. 

However, if your home doesn't have good airflow, it may already be showing signs of damp and high humidity: a musty odour, condensation on windows, or mould. 

The different types of dehumidifiers

There are two main types of dehumidifiers: refrigerants and desiccants. 

Refrigerant dehumidifiers

"These use the same technology as a fridge," says Chris. "They draw in air, cool it to condense the water it contains, then warm it and blow it back out. 

"It's easier for them to cool the air if it's already warm, so they work best in moderate or warmer climates. However, the released warmer air might be undesirable in hot climates."

Refrigerant models tested in our dehumidifier product reviews were more energy efficient than desiccant models, had larger tanks and better water removal. But they were also larger, heavier and noisier.

Desiccant dehumidifiers

"These models use a slowly rotating disc or belt of material that absorbs moisture from the air," says Chris. "The damp section then moves through a drying process, which evaporates the water and collects it in a tank."

Desiccant models tend to perform similarly no matter what the air temperature is, so can be better in cooler climates, where a refrigerant model may struggle. However, in a warm or hot climate, "a refrigerant will usually outperform a desiccant", says Chris.

The desiccants we tested typically had a higher running cost and smaller tanks, but tended to be lighter, compact and more portable. 

Are dehumidifiers good for drying clothes?

Research suggests drying clothes indoors can increase the chance of dust mites and mould spores in your home, which can have a negative impact on your health. 

The laundry function on many dehumidifiers helps dry washing more efficiently indoors by pulling excess moisture from the air. They're no match for tumble dryers, but they're still a great option if you don't have outdoor drying space, especially during colder months.

"The moisture has to go somewhere, and if your home doesn't have good airflow to let moist air escape, you can end up with damp walls and furniture – perfect conditions for mould," says Chris. "A dehumidifier can speed up indoor clothes drying and make it safer."

What should I look for when buying a dehumidifier?

First off, consider where you'll be putting it. 

"In colder areas (say, below 20°C), a desiccant model may be best, and for warmer areas, consider a refrigerant model," says Chris. 

Other features to consider include energy efficiency, running costs and water-removal effectiveness, as well as the tank size – ideally it should hold at least four litres of water so you're not constantly emptying it. 

"If you'll be running the dehumidifier a lot, a model with continuous drain might be useful," adds Chris. 

Also consider noise, especially if it's intended for bedrooms or living areas.

cat next to dehumidifier

Not purrfect: If the room is very damp, you might need a bigger dehumidifier.

What size dehumidifier do I need?

A model with a higher capacity tank will tackle moisture problems faster, especially in a larger room. Most models have a recommended room size, so check this when shopping around. 

"It also depends on how damp the room is," says Chris. "Look at the rated water-removal rate and scale up if the room is unusually damp. For a regular-sized room (say, 30m2) you might usually need a 20L model, but if it's very damp, you might want to consider a slightly bigger model."

However, size affects weight. Larger dehumidifiers can weigh up to 20kg – not ideal if you're carting it up and down stairs.

How much do they cost?

Models can range from $300 up to about $750 and, based on our performance testing, reliable models will cost an average of $540.

But you'll also want to consider ongoing expenses. In terms of running costs, models can range from two cents to 21 cents per hour, which can soon add up. Aim for a balance between running costs and water-removal effectiveness.

We care about accuracy. See something that's not quite right in this article? Let us know or read more about fact-checking at CHOICE