I tested a smart dehumidifier in my damp bedroom – and the results surprised me

Princess is best known for affordable, well-designed kitchen and home appliances, and dehumidifiers are very much part of that offering. I’ve been testing the Princess Smart 20L, available at B&Q for just over a month in my period home, including a bedroom that’s always been a bit of a problem when it comes to damp.

With thick walls and limited ventilation at this time of year, it’s exactly the kind of space where condensation builds up quickly, and mould can creep in if you’re not careful. In other words, a pretty realistic setting for seeing how this high-capacity, smart-controlled dehumidifier copes in day-to-day life.

The best dehumidifiers bring humidity down, stop damp in its tracks and are simple to manage day to day. So when I tested the Princess Smart 20L dehumidifier, I put it through the same checks we use for every model to see how well it handled moisture control and how convenient it was to live with, including how easy it was to 'set-and-forget' with its smart app control.

At a glance

Princess is a well-established consumer appliances brand, particularly popular across Europe, and best known for making affordable, well-designed home gadgets that aim to make everyday tasks easier.

The Princess Smart 20L dehumidifier sits at the larger end of the brand’s dehumidifier lineup and is designed to tackle higher humidity levels in real homes, including older properties like mine. I tested it over a month in a period house with thick walls that’s prone to condensation, damp, and occasional mould, especially during the colder months when ventilation is limited.

What sets this model apart is its smart functionality. Alongside manual controls, it can be operated via the Princess app, letting you monitor humidity levels, adjust fan speeds, set schedules and turn the unit on or off remotely. In everyday use, that made it easy to keep humidity in check without constantly interacting with the machine itself. It felt straightforward to live with, quietly working away in the background while giving me the option to step in and fine-tune settings when I needed to.

Specifications

• RRP: £230.00
• Type: Compressor
• Colours: White
• Extraction rate: 20L/day
• Water tank capacity: 3.7L
• Max room size recommended: 20m squared
• Noise level: 39dB – 44dB
• Power: 325W
• Dimensions: H57.2x W34.4 x D25cm
• Weight: 12kg
• Portable?: Yes
• Automatic humidity sensor: Yes
• Continuous drain option: Yes (hose included)
• Laundry mode: No
• WiFi connectivity: Yes
• Timer: Yes
• Child lock: No
• HEPA filter: No
• Warranty: 2 years

How I tested

I tested the Princess Smart 20L dehumidifier in my home over the course of a month, using it in different rooms to see how it coped with varying conditions. This included a damp bedroom that’s prone to condensation, as well as drier parts of the house, to get a sense of how it performed across the home.

To check accuracy, I used an independent humidity monitor and compared its readings with the humidity levels shown on the dehumidifier display and in the Princess app.

I tested how easy it was to set schedules and adjust settings using the app, as well as how intuitive the manual controls were in day-to-day use. Noise levels were measured on both fan settings using a decibel meter, and I paid close attention to how noticeable the dehumidifier was during normal daily activities.

As part of regular use, I checked how easy it was to empty the water tank and remove the filter, as these are tasks you’ll need to do routinely. By using the dehumidifier in different rooms, under different humidity levels, and over an extended period, I was able to get a clear picture of how easy it is to live with and how well it performs in a real home.

Unboxing, set-up and design

The Princess Smart 20L arrived in a large cardboard box, with additional cardboard packaging inside to keep the unit secure. The dehumidifier itself was wrapped in protective plastic, which did its job well, although whether that plastic is recyclable will depend on the services in your area.

Inside the box is the dehumidifier, the instruction manual, and a hose for continuous drainage. Everything is neatly packed and easy to remove, and there’s nothing over-the-top or fiddly about the packaging. It’s a straightforward unboxing that gets you up and running quickly.

Set-up

Getting the Princess Smart 20L ready to use is refreshingly simple. The filter is already in place, the castor wheels are pre-attached, and there’s very little to do beyond positioning it and switching it on.

The manual recommends leaving around 20cm of clearance between the unit and walls or other obstacles, and avoiding direct sunlight. Once positioned, you can control it using the top panel or the Princess app, available on Android and iOS. It also works with Google Assistant if that's your preference.

Connecting it is as simple as downloading the Princess app, connecting to Wi-Fi, creating an account and adding the device, all of which took just a few minutes. Having struggled with connecting smart devices in the past, this felt like a breeze in comparison.

Using the app, you can turn the dehumidifier on and off remotely, adjust fan speeds and set humidity levels, schedules and timers. The app also displays the current humidity level of the room, which means you can check conditions while you’re out. If humidity creeps up while you’re at work, you can switch it on remotely and come home to a more comfortable indoor climate.

In terms of looks, the Princess Smart 20L is taller than most dehumidifiers, measuring around 57cm in height. That said, it’s not very deep or wide, measuring 25cm by 34.4cm.

It comes in a sleek black-and-white colourway, with a smooth, shiny white plastic casing on the front and back, black side panels, and a black control panel on top. Some of the finishes are glossy, others matte, and overall it looks and feels minimalist and more premium than I expected.

At the back of the unit, you’ll find the vented panel where the filter is housed, along with the drainage tank.

Despite its size, it’s easy to move thanks to the built-in wheels and two well-concealed side handles, which are neatly integrated into the black panels.

I really like the modern, minimalist display. When the unit is switched off, it’s almost completely hidden within the black panel. Once powered on, it clearly shows the current humidity level, fan speed, timer settings and active modes.

There’s also a swing function, which allows the air outlet at the top of the unit to move up and down continuously, helping to circulate air more evenly around the room. You can set a timer between one and 24 hours, and switching between fan speeds and modes is intuitive using the touch controls.

The drainage tank has a capacity of 3.7 litres. That’s a good balance between capacity and overall size, meaning you won’t be emptying it constantly, but it’s still easy to handle when full.

Once the tank fills up, the dehumidifier stops automatically to prevent overflow and beeps at you until you remove and empty it. If you’d rather not empty the tank manually, you can use the included hose for continuous drainage, which allows the unit to extract up to 20 litres per day. The hose measures around 73cm. It could be longer, but it’s perfectly functional.

The tank itself is very easy to remove and replace. There’s a simple handhold that makes it easy to pull out and reinsert. Accessing the filter is a little more fiddly, as it involves removing a perforated panel, but it’s not something you’ll need to do often.

Ease of use

The Princess Smart 20L dehumidifier is easy to live with on a day-to-day basis. Whether you’re using the controls on the unit itself or the app, everything feels intuitive and well laid out.

Using the app, you can check the current humidity level, set a target between 40% and 80%, adjust fan speeds, set timers and schedules, and turn the unit on or off remotely. It’s quick to respond and easy to navigate, which makes it genuinely useful rather than just a novelty.

On the unit, the display is clean and minimalist, clearly showing humidity levels, fan speed, timer settings and active modes at a glance. The touch controls respond well, and switching between settings only takes a few taps. The swing feature allows the air outlet at the top of the unit to move up and down continuously, helping to circulate air more evenly around the room.

Practical details also help with everyday use. The castor wheels and concealed side handles make it easy to move between rooms, while the water tank is simple to remove and empty when full. Filter access is slightly more involved, but it’s not something you’ll need to do often.

There are a couple of omissions worth noting. There’s no child lock, which would be useful in family homes, and there’s no dedicated laundry mode, so drying clothes relies on manual settings rather than a one-touch programme.

Overall, the Princess Smart 20L dehumidifier combines straightforward controls with genuinely useful smart features, and while it lacks a few extras, it's easy and intuitive to use in everyday life.

Performance

I started testing the Princess Smart 20L in a bedroom that’s always been tricky when it comes to damp. It has two external walls, which makes it far more prone to higher humidity, condensation and the kind of damp patches that tend to show up in corners. We’ve had mould issues here in the past, so this felt like a proper stress test.

Before switching it on, humidity levels were sitting at just over 80%, which is very high. I ran the dehumidifier for an hour at full power, using the high fan speed with the swing function on, and checked both the humidity level and how much water had collected. After that first hour, humidity had dropped to around 60%, with about 100ml of water pulled from the air.

I left it running for another hour under the same settings. By the end of the second hour, the humidity level was still holding steady at 60%, and the tank contained around 300ml of water in total. On other occasions in this same room, I managed to bring humidity down even further, to around 55%, which sits nicely within the generally accepted comfortable range for a home and immediately made the room feel fresher and less dank.

I then repeated the test in a room with just one external wall, which tends to be much drier. Here, humidity levels started at around 67%. Under the same settings, the Princess Smart 20L brought humidity down to 55% in just half an hour, and by the end of the first hour had removed around 200ml of water, while comfortably maintaining that lower level.

Overall, the Princess responded quickly to changes in humidity, working hardest where conditions were worst and easing off in drier rooms. It felt particularly effective in problem spaces, while still being efficient and controlled in rooms that needed less intervention.

Energy use

If you're wondering how much a dehumidifier costs to run, it largely depends on its wattage. The higher the wattage is, the more energy it uses.

The Princess Smart 20L dehumidifier has a power rating of around 0.33kWh, which works out to roughly 9p per hour to run. It’s not the cheapest dehumidifier on the market in terms of energy use, but it sits firmly in the middle for a smart 20-litre model. Based on this figure, running the Princess Smart for 12 hours would cost about £1.08

During testing, it felt affordable enough to run regularly without worrying about energy bills creeping up too quickly, particularly if you’re using schedules or switching it on only when humidity levels rise.

Noise levels

The stated average noise level in the manual is 46dB. In real-world use, I measured around 39dB on the lowest fan setting and roughly 44dB on the highest, using a decibel reading app on my phone. That’s comparable to a quiet office or library.

Overall, it’s pretty unobtrusive during the day, though the higher fan speed may be noticeable if you’re trying to sleep nearby.

Portability

Despite being a fairly large, high-capacity dehumidifier, the Princess Smart 20L is easy to move around the home. It comes with built-in wheels, which are already attached out of the box, so there’s no setup required before rolling it into position.

There are also two concealed handles on either side of the unit, neatly integrated into the black side panels. These make it easier to move the dehumidifier between rooms when combined with the wheels.

While it’s not a lightweight machine, it never felt awkward to move during testing. I was able to use it in both a damp bedroom and a drier living room without it feeling like a hassle to relocate, which makes it practical if you want to tackle humidity in different parts of the house rather than leaving it fixed in one place.

Maintenance

Day-to-day maintenance on the Princess Smart 20L dehumidifier is simple and doesn’t take much effort. The water tank is easy to remove and empty, with a straightforward handle that makes it quick to pull out and slot back into place once emptied.

Accessing the filter is slightly more involved, as it sits behind a perforated panel at the back of the unit. That said, it’s not something you need to do often, and once the panel is removed, the filter itself is easy to take out and refit.

Because the dehumidifier stops automatically when the tank is full, there’s no risk of overflow, which also helps keep maintenance stress-free. Overall, routine upkeep feels manageable rather than fiddly, and nothing about the process stood out as awkward during regular use.

How it compares with other dehumidifiers

To put the Princess Smart 20L into context, it helps to look at how it stacks up against a few other popular dehumidifiers we've reviewed recently.

If you compare the Princess Smart 20L with the MeacoDry Arete One 12L, the biggest difference really comes down to size and what they’re designed to do. The Meaco is well-suited to smaller spaces, offering quiet, straightforward moisture control that works nicely in bedrooms, flats and compact rooms. It also includes extras like a HEPA filter and a child lock, which the Princess doesn’t offer. The Princess, by contrast, is built to handle much higher humidity levels, making it a better fit for larger rooms or more persistent damp. Its smart app control also means you can check humidity levels and adjust settings without needing to be in the same room.

When you look at the DREO Smart 512S, there are plenty of similarities on paper, particularly around smart features and app control. The DREO is often praised for its clear humidity feedback in the app and family-friendly extras like a child lock. However, it’s a little noisier during operation, the water tank is a little smaller at 3.4 litres, and our reviewer found it kicked out quite a bit of heat during use, so it may not be suitable during the summer months.

When you compare the Princess 20L with another smart dehumidifier designed for larger living spaces, the Duux Bora Smart 20L is more expensive to run, costing around 12p per hour compared with the Princess’s 9p per hour. That higher running cost does bring added benefits, though, including a built-in carbon filter designed to help reduce airborne pollutants such as bacteria and tackle lingering odours from damp, smoke, cooking smells, or pets.

How does it rate online?

The Princess 20L dehumidifier has 3.7 out of 5 stars from 18 ratings on Amazon, with 57% of reviewers giving it 4 stars or above. Feedback from buyers is generally positive, with most reviewers agreeing that it does a solid job of pulling moisture out of the air. Several customers describe it as a “great dehumidifier” that’s effective when left running for longer periods, particularly in damp-prone rooms. The smart features also get a thumbs up, with one reviewer saying it’s “handy to have it controllable from my phone”, making it easier to tweak settings without constantly fiddling with the controls on the unit itself.

Some reviewers do flag concerns around longevity and noise on higher settings, which brings the overall score down, with one noting that it “stopped working after about 14 months”, despite performing well up to that point. Others flag that it’s on the heavier side.

Overall, though, reviews suggest it’s a capable, well-featured dehumidifier for the money, as long as you’re aware of a few trade-offs.

Should you buy it?

After a month of real-world testing in my period home, the Princess Smart 20L proved itself as a strong option for tackling serious damp. It brought humidity down quickly in problem rooms, kept condensation under control, and made my home feel noticeably more comfortable.

The smart app worked reliably, making it genuinely easy to set schedules, monitor humidity remotely and let the machine quietly get on with the job without constant input.

It’s not without compromises. The unit is larger and heavier than compact models, and while noise levels are reasonable for a 20L dehumidifier, the higher fan setting is noticeable if you’re trying to sleep nearby. There’s also no dedicated laundry mode or child lock, which some households may miss.

Compared with smaller models like the MeacoDry Arete One 12L, the Princess is bigger, more powerful and better suited to persistent damp, while remaining affordable to run at around 9p per hour. More premium smart alternatives, such as the Duux Bora Smart 20L, offer extras like air filtration but cost more to run.

If you’re dealing with higher humidity in a larger room or older home and want smart control without premium running costs, the Princess Smart 20L strikes a strong balance between performance, convenience and value.