6 things you need to know before buying a dehumidifier – I'm a home tech editor and here's how to make sure yours is the right for your home

Dehumidifiers are superb at tackling damp, mold, mildew and most other excessive moisture issues in the home. But they can be pricey investments, especially when you're aiming for all the bells and whistles.

Understanding the different types of dehumidifiers, their common features and functions will help inform your decision picking the right dehumidifier. Until you've used one and know what a dehumidifier does, it's hard to know what to look out for and what to avoid.

I'm H&G's home tech editor and I regularly test appliances like dehumidifiers and purifiers, but I also caught up with a couple of veteran HVAC experts to find out the key things to know before buying a dehumidifier.

Things I wish I knew before buying a dehumidifier

Once you get to grips with the following to work out how long it will take a dehumidifier to dry out a room, you'll easily find the right dehumidifier for your home and to best suits your needs.

1. There are different types

The most popular dehumidifier you'll find is a compressor one, which essentially uses condensation to remove humidity from the air. It has coils, which are cooled for the warm, moist air to condense against.

Another common dehumidifier type is a desiccant dehumidifier. Instead of condensing the moisture, a desiccant dehumidifier absorbs the moisture using a wheel that acts similarly to an extractor fan or sponge. A heater and fan work consistently to regenerate this element for continued use.

The main difference here comes down to where you place your dehumidifier and when you're using it. Compressor dehumidifiers work best in warm environments as the coils work less efficiently in cooler temps (60°F or less). Desiccant dehumidifiers work year-round and tend to be lighter and quieter, but don't typically have the high extraction rates of compressor dehumidifiers.

So, desiccants are ideal for colder rooms like basements, while compressors are better for inside the home. Desiccant dehumidifiers can also release warmer air into the room, helping to further dry those cold, wet areas.

You can also find non-electric dehumidifiers. They aren't nearly as effective but they can provide affordable, small-scale dehumidifying if you don't need as much power. I use one in my car for example, and it removes overnight moisture so that the windows are clear in the morning.

2. Get the right size

Like the best air purifiers, a dehumidifier's size dictates how much indoor space it can cover. You'll also want to consider its capacity too; as most dehumidifiers need to be emptied manually, the bigger the tank is, the less often you have to empty it.

'Choosing the wrong size can frustrate you if the unit can't keep up with the moisture in your space,' says Josh Mitchell, seasoned HVAC technician from Air Conditioner Lab.

Josh adds that dehumidifiers are usually measured in 'pints per day' – measuring how much water it can remove from the air over time. 'A small 20-pint model works well for bedrooms or closets, but larger spaces like basements need at least a 50-pint unit,' Josh advises.

3. You don't have to drain it yourself

As a dehumidifier turns the moisture in the air into liquid in a water tank, it needs to be emptied. Usually this is something you'll do whenever it gets full (and most dehumidifiers will stop operating once the tank is full), but there are models with self-draining systems. If you think your dehumidifier's going to get a lot of use, it's worth considering so you can set it and forget it.

'If you don't want to empty the water tank daily, choose a model with a built-in pump or continuous drain option,' explains Josh.

A continuous drain setting works by attaching a hose from the dehumidifier to a drain, then gravity does the work. But if you invest in a dehumidifier with a pump, it will automatically drain the water once it reaches a certain level, and can empty it vertically or horizontally.

If you have a floor drain or low access to a water outlet, a dehumidifier with continuous drain is all you need. If not, spend a bit extra for a self-draining pump. It'll make all the difference.

4. Humidity settings help

Cheaper models, like this budget dehumidifier from Amazon that our writer found kicked condensation to the curb are able to remove moisture from the air but won't always be able to achieve the right relative humidity (RH).

What a dehumidifier does is remove moisture from the air. But not all dehumidifiers have an accurate humidistat to be able to reach a desired relative humidity (RH), 'between 30% and 50% is ideal for comfort', according to HVAC pro Josh Mitchell.

'When the air in a home is too dry, it typically contains more irritants and pathogens, which are better to avoid for people with respiratory diseases, particularly allergies,' explains Glenn Gault, CEO of Gault Heating & Cooling.

Too humid air is a favorable environment for mold and mildew growth, which is also bad, because mold and mildew are serious allergens.'

A dehumidifier without humidity control can easily leave the room either too dry or too humid, so it's worth opting for one with more control, even it costs a little extra.

5. Think about noise and energy levels

You might start getting annoyed at your choice if your dehumidifier is constantly disturbing your sleep, work or relaxation time due to its noise level when operating.

'Most dehumidifiers, especially larger ones, emit a noticeable hum,' says Josh. 'Check the decibel rating if you place it in a living area or bedroom. Anything below 50 dB is relatively quiet.'

You can also find ones with dedicated sleep modes with quieter operation.

A dehumidifier, like any electrical appliance, will also cost you to keep running. Over time, the energy efficiency of your unit will influence how much you're paying in bills, so it's a smart move to choose one that's efficient, even if the initial outlay is more.

'Dehumidifiers can be energy-intensive if used regularly,' Josh Mitchell adds, so it's important to look for those with an ENERGY STAR rating.

6. Extra features make a difference

This is strong advice when buying any long-term appliance, but read into what extra features are available, to see if they're worth the spend by making your life easier.

An example would be air purification, so instead of having both a dehumidifier and air purifier, you can choose a dehumidifier that does both, saving floor space and the cost of another unit. Look for ones with HEPA filters for effective air purification.

A special laundry mode is a savior when you're looking for ways to dry clothes quickly with your dehumidifier. It'll increase fan speed in a localized area to minimize laundry drying time, which will make a difference come winter.

The Frigidaire Gallery 50-Pint Dehumidifier we've reviewed has WiFi connectivity and app controls, which means you can safely use and monitor your dehumidifier when you're not in the room.

If you're not choosing with one that self drains, this is a great way of notifying yourself every time you need to empty it as it'll pause itself when it's full.

My top dehumidifier picks

Next, find out how to make DIY dehumidifiers for mild moisture control around the whole house, and whether you should a dehumidifier during the day or at night.