Dehumidifier questions, answered

July 4th, 2016

Appliance Talk Buying Guide Dehumidifiers

Dehumidifier questions, answered

Looking into buying a dehumidifier? This guide provides answers to several dehumidifier questions, to help you keep your home’s air clean, clear and free from excess moisture.


What’s the ideal humidity level to set on my dehumidifier?

According to the National Asthma Council of Australia…

“Indoor relative humidity should be maintained between 30 and 50 percent if possible. This is the range that is most comfortable for people, but not for dust mites or mould.”

Even if you don’t have asthma or allergies, these are still good guidelines to follow. Dust mites and mould thrive in areas of high humidity, and breathing these in is always a Bad Thing.

Mold on wall and ceilingsource: Infrogmation of New Orleans on Wikimedia Commons

And if the air in your home is too dry, you increase your risk of catching viruses, such as colds and flu (especially true in the low-temperature winter months), not to mention nosebleeds and sore throats. Plus, an overly-dry environment can have an effect on surfaces through your home, even leading to cracks and flaking in some cases.

This doesn’t mean that you should always run your dehumidifier at 30% – doing so could be an inefficient waste of energy. A dehumidifier is a bit like an air conditioner in that you need to take your local conditions into account. You CAN use an air conditioner to bring your living room to an icy, freezer-like temperature on a scorching summer day, but it’ll take a lot of work and use up a whole TON of energy. Similarly, try to aim for a realistic humidity level relative to your room’s current humidity, so your dehumidifier won’t waste energy overexerting itself in pursuit of an impossible goal.

Of course, there’s also comfort to consider. While cooler winter months can be rainy and misty, these conditions often feel much more tolerable than those of a hot and sticky summer day.

For a general guideline of which dehumidifier settings will feel most comfortable in different conditions, check out this table, based on the Comfort Mode of the Dimplex GDDEU30:


Humidity Level

5°C to 20°C
20°C to 27°C 55%
27+°C 50%


How is a dehumidifier’s performance measured? And is it accurate?

You can compare the performance of different dehumidifier models by looking at their dehumidification capacity – the amount of moisture they can remove from the air in 24 hours under testing conditions.

Goldair GD275 DehumidifierGoldair GD275 Dehumidifier

According to NZ dehumidifier manufacturer Goldair, the worldwide standard for testing dehumidifier performance is an environment of 30°C and 80% relative humidity. Manufacturers run their products in this environment for 24 hours, and look at the amount of water they produce to determine their dehumidification capacity.


But unless you live in an appliance testing facility, your home won’t experience environmental conditions like these all the time. In an environment with a lower temperature and/or lower relative humidity, you may experience slightly lower performance from your dehumidifier. It’ll still do a good job – just don’t be surprised if your at-home scientific testing doesn’t precisely match up with the specifications!

How powerful a dehumidifier do you need?

Working out the right size/power level for an appliance along the lines of an air conditioner or a fridge is relatively easy – just compare the capacity or performance to the size of your home. But what about dehumidifiers?

Check out the following dehumidifier chart for an approximate size guideline, comparing the size of your room in square metres (the floorplan tool in Panasonic’s Air Conditioner Sizing Wizard provides a quick and simple way to get this measurement), and the litres of moisture the dehumidifier can remove from your home’s air over 24 hours:

Approx humidity

46 sqm

93 sqm

139 sqm

186 sqm

232 sqm

279 sqm

325 sqm

325+ sqm

Moderately damp (50% to 60%) – Space feels damp and has musty odour only in humid weather. 5L/day 7L/day 9L/day 10L/day 12L/day 14L/day 17L/day 19L/day
Very damp (60% to 70%) – Space always feels damp and has musty odour. Damp spots show on walls and floor. 6L/day 8L/day 10L/day 13L/day 15L/day 19L/day 21L/day 24L/day
Wet (70% to 85%) – Space feels and smells wet. Walls or floor sweat, or seepage is present. 7L/day 9L/day 12L/day 15L/day 18L/day 21L/day 24L/day 28L/day
Extremely wet (85% to 100%) – Laundry drying, wet floor, high load conditions. 8L/day 11L/day 12L/day 15L/day 18L/day 21L/day 24L/day 28L/day

Please consider these somewhat random-looking measurements to be approximate guidelines, as they were originally sourced from the US-based Association of Home Appliance Manufacturers (AHAM) and converted from room size measurements in square feet, and volumes in pints per 24 hours. Not Imperial Pints, either, but US Liquid Pints. Sorry Americans, but learn to metric, please.

grandpa metricsource:

Do you still need a dehumidifier if you have air conditioning?

In many cases, no. Many air conditioners effectively double as dehumidifiers and air purifiers, while cooling or warming your home’s air. This is especially true if you’ve sprung for one of the larger split systems.

Dimplex-DC15RCBW-Hero-highDimplex DC15RCBW 4.4kW Portable 4 in 1 Air Con

But if you have a separate laundry room, a basement, or a spare room tucked away in a distant corner of the house that the air conditioner doesn’t quite reach, these “out of sight, out of mind” spots could develop problems with humidity, and turn into breeding grounds for the growth and spread of mould, mildew and other nasty allergens.


As these areas aren’t typically everyday living spaces, it’s probably not worth giving them their own air conditioning – why cool/heat an area that’s not being used? But to prevent sickness-spreading nasties from taking up residence in these tricky spots, a dehumidifier could be just the thing.

Can I dry clothes with a dehumidifier?

Here’s one weird trick (that trainers hate) for drying your clothes on a cold and rainy day, if you don’t have access to a dryer. Basically, stick your dehumidifier in the room where you hang up your clothes indoors, to help accelerate their drying process.


To get the best drying results, you may want to run the dehumidifier in a slightly different way to normal – instead of entering your chosen humidity level (say, 50%), set it to Continuous operation at its highest setting, to extract the maximum amount of moisture from your dripping wet clothes!

Keep in mind that using a dehumidifier this way will likely fill up its internal tank much more quickly than normal, so it may be worth attaching a hose and setting it to Continuous Drain mode if possible. Also, this isn’t the most energy-efficient way to use your dehumidifier, so be extra-careful not to forget about it and leave it running all night!

How much does a dehumidifier cost per hour to run?

Like any appliance, it all depends on how you use it and the price of electricity in your area.

Aus money

For example only, using an average energy rate of 33c per kWh (as per guidelines from the South Australian government), then the 16L Goldair dehumidifier with a wattage of 410W should cost just 14c per hour to use on average.

The exact cost will always vary, though, depending on exactly how you use your dehumidifier, the peak and off-peak energy tariffs in your area, and your local climate.

Do dehumidifiers also kill germs?

Some, but not all of them do.

While most dehumidifiers will include a basic filter to help keep dust and grots out of their inner workings, some also include an antibacterial filter to remove germs and allergens (pollens, spores etc) from the air as well as moisture.

Delonghi AriaDry Compact Dehumidifier 25L DDS25The Delonghi AriaDry Compact Dehumidifier 25L DDS25, (featuring an antibacterial air filter)

A few dehumidifiers also include an ionising function, which involves using UV light to kill off more bacteria as it passes through the unit, allowing you and your loved ones to breathe easier.

If the primary reason for buying a dehumidifier is to protect your household from nasties, then it’s definitely a good idea to look for a potential dehumidifier that includes antibacterial filters as well as a decent dehumidification capacity.

Can I drink the water from my dehumidifier?

As tempting as that may sound, it’s probably a bad idea. The water that comes out of your dehumidifier is made up of condensed moisture from your home’s air, and as it isn’t treated or purified, it could contain impurities and germs.

drinking the watersource:

If you have a garden, the water should be just fine for your flowers and other decorative plants. But just in case, it’s best not to use it on vegetables or trees with fruit that you’re planning to eat.

Can I use a dehumidifier in the bathroom?

Yes, but you’ll want to be careful with it. The water-rich environment of a bathroom, combined with any electrical appliance, can result in Having A Bad Time if you’re careless.

Keeping humidity under control in a bathroom is important, especially during the winter months, as hot steam from your shower can cling to cool wall surfaces, creating an ideal breeding ground for mould and mildew. While windows, ventilation and extractor fans already do a pretty god job of removing steam from bathrooms, a dehumidifier can be handy for eliminating any humidity that gets left behind.

nasty mould in the bathroomsource: Milliped on Wikimedia Commons

To avoid overtaxing your dehumidifier and wasting energy, wait for most of the steam from your shower to exit the bathroom before running the dehumidifier, which should help reduce the level of moisture in the air and on your bathroom’s surfaces, limiting the growth and spread of mould. Just be very careful to keep the dehumidifier and its power supply well away from water sources, and remove it from the room while you’re showering.

Will a dehumidifier cool down your home?

Nope! In fact, most do the opposite.

Like any other electrical appliance, dehumidifiers emit some waste heat while operating. This may sound a bit like an unintentional bonus feature that could come in handy on cool, wet winter evenings, but a dehumidifier’s level of heat is nothing compared to a properly-functioning heater or reverse-cycle air conditioner.

Sunbeam-Ceramic-Electric-Fan-Heater-HE2105-highSunbeam Ceramic Electric Fan Heater HE2105

Keep this in mind when running a dehumidifier during sticky summer months. It’ll help keep your home dry and comfortable, but to actually lower the temeprature, you’ll need an air conditioner.

Where’s the best place to set up my dehumidifier?

Honestly, your dehumidifier’s placement doesn’t really matter that much. You can set up a dehumidifier in most places around the home, whether that’s by a wall, under a table, or discreetly tucked out of the way.

Bubble wrap, kitchen roll and air dehumidifierSpot the dehumidifier! (source: Stanze on Flickr)

That said, a dehumidifier does its best work when it has access to a fair amount of unrestricted airflow, so setting it up in a cabinet, cupboard or some similar enclosed space would probably not be the best idea.

Can a dehumidifier help to control fleas?

Not on its own, but it can be helpful for keeping fleas under control.


Much like dust mites, fleas tend to prefer humid environment if possible. By using a dehumidifier to restrict fleas’ easy access to life-giving moisture, you’re one step closer to banishing them from your home.

But a dehumidifier won’t be able to eliminate fleas all on its own. Using one properly in conjunction with regular vacuuming throughout your home and properly bathing and/or grooming your pets will go a long way towards getting rid of the little nasties.

Can I dry new plaster with a dehumidifier?

Let’s say you’re an aspiring DIY guru and you’ve just laid down a fresh layer of plaster. If you want to speed up its drying process, would a dehumidifier be able to help? And what about the same scenario, but with wet paint? Or freshly-cleaned carpet?


The answer is – yes, but you need to be careful.

Natural drying is almost always the best solution, even if it’s not always the fastest. While a dehumidifier would certainly help to speed the drying of damp surfaces, especially on cold and rainy days, you run the risk of having the surfaces dry unevenly, depending on the airflow through your home, leaving some patches dry and other still dripping wet. And if you over-dry a room, you risk premature cracks and flaking. Be smart!

How noisy or quiet are dehumidifiers?

A dehumidifier’s noise level depends partly on the model, and partly on where you set it up.


Most dehumidifiers are unlikely to be much louder or quieter than a typical air conditioner or portable fan, though on top of the noise of their motor, you may occasionally hear a bit of a drip as some condensed water is dispensed into the tank.

Like all appliances, the amount of noise a dehumidifier makes can be made louder or softer by the acoustics of its surroundings. Solid surfaces that echo, or unstable surfaces that amplify vibrations may make your dehumidifier sound louder than it actually is. On the other hand, soft surfaces that absorb sounds and vibrations can help to reduce a dehumidiifer’s noise level. If noise is a concern for you, keep this in mind when setting up your dehumidifier.

Thoughts on dehumidifiers? Questions, comments or problems? Please share!

Mark joined Appliances Online in November 2011 and has since learned more than he ever expected to know about appliances. He enjoys looking for new and unusual ways for to solve everyday problems using typical household appliances. When he’s not toiling at the desks of Appliances Online and Big Brown Box, he tries to find time to write the next big bestseller and draw satirical cartoons, but is too easily distracted by TV, music and video games. Mark’s favourite appliance is the Dyson Groom Tool, as he loves the concept of vacuuming your dog. Google+

Leave a Reply

Your email address will not be published. Required fields are marked *