How we test dehumidifiers: The Expert Reviews testing methodology explained

If your home suffers from excessive moisture, leading to damp walls, wet windows and mould, a dehumidifier could be the answer. Ditto if you’re looking for another way to dry your laundry without adding to your damp problems or over-using the tumble dryer. However, while all dehumidifiers do the same basic job – drying moisture from the air – there are big differences in how effectively they do it, how easy they are to use, how much noise they output and how much energy they use.

As far as we’re concerned, these factors make the difference between a great dehumidifier you’ll use frequently to keep moisture under control, and one you’ll regret buying. To find out which is which, we run every dehumidifier through a series of tests that evaluate each major aspect of their performance.

How we test dehumidifiers: Setup and basic usability

We begin each test by unboxing the unit, removing any tapes or additional packaging and inserting any air filters provided, according to the instructions.

We then turn the dehumidifier on and start looking at its modes and features. Throughout the review process, we’ll look at how quick and intuitive it is to switch between modes, or to set the target humidity level. We’ll also look at simple practical concerns, like how easy it is to move the dehumidifier from room to room, and whether there are any constraints around where it’s used: can it be placed out of the way close to a wall, or does it need to sit in the centre of a room? Here, we’ll refer to the instructions for guidance.

Where a dehumidifier has smart features, we’ll also install the companion app and connect the dehumidifier to a Wi-Fi 6 home network, so that we can see whether they’re worth using, and what practical benefits they bring.

How we test dehumidifiers: Performance testing

We test dehumidifiers in real-world situations inside a three bedroom house over several days to get a clear picture of its modes and features and how well they work.

We use two rooms for specific tests; a large living room that’s prone to damp and mould, and the other a small, single bedroom in the North-East corner of the house, that doesn’t get much sun. We try to keep both rooms at a comfortable 19-20°C temperature before and during testing. We use a wireless air-quality monitor backed up by a temperature and humidity meter (hygrometer) to measure the relative humidity (RH), then set the dehumidifier to run with a 50% RH target on the highest fan setting. We then measure the RH after one hour and then again after a second hour, to see how quickly and effectively the dehumidifier works.

After these tests, we’ll use the dehumidifier in these rooms and other rooms around the house to see how well it works in different situations, and how effective it is at keeping humidity levels under control. We’ll also use the dehumidifier to dry a rack full of recently spin-dried washing of different materials and weights, to find out whether its laundry mode makes the grade. We’ll run the laundry program for its default time, or for eight hours if there isn’t one. Any dehumidifiers with particularly stand out performances, we list on our Best dehumidifier for drying clothes roundup.

How we test dehumidifiers: Noise and power consumption

During testing, we’ll also use a smartphone sound meter to measure the noise output on its highest and lowest fan settings. We’ll also use a plug-through power meter to measure how many watts it consumes at both extremes.

How we test dehumidifiers: Refining our tests

Sticking to a consistent methodology means we can compare dehumidifiers over several years – an essential in a market where successful products can remain on sale for five years or even longer. However, that doesn’t mean we don’t consider adjustments and changes over time, in order to test new features and technology or reflect feedback from readers and manufacturers.