Knowing how to choose a dehumidifier usually starts with a problem you can already see. Windows stream on cold mornings, towels stay faintly damp and the spare room has a musty smell that lingers.
The right unit depends on how warm the room stays, how much space it covers and how much moisture your household creates. This guide walks through each decision in order, so you buy for your home, not the biggest number on the box.
Start With the Room You Need to Dry
Understanding the room first saves you buying the wrong machine.
Look for Signs of Condensation Damp
Condensation is the most common form of damp in homes. It forms when moisture from showering, cooking and drying laundry settles on colder surfaces such as window frames, corners and walls behind wardrobes. Wet glass, a musty smell and slow-drying washing are classic signs that a dehumidifier can help.
Rule Out Leaks and Rising Damp
Rain getting through a wall, leaking pipes and rising damp are building faults. A dehumidifier can take moisture out of the air, but it cannot repair a roof or a failed damp proof course. If a patch keeps returning in one spot, call a qualified damp surveyor first.
Note How Cold the Room Gets
Leave a basic thermometer in the room for a few winter days. A heated bedroom and an unheated garage need different types of dehumidifier, so this reading shapes your choice.
Choose Between Compressor and Desiccant
The two main types remove moisture in different ways, and room temperature usually decides which one fits. For a closer look at the mechanics, read how does a dehumidifier work.
When a Compressor Model Makes Sense
Electrical Safety First explains that compressor models, also called refrigerant models, pass moist air over cold coils so the water condenses and collects in a tank. They work best in warmer temperatures and are generally more energy efficient in those conditions. That makes them a good fit for heated bedrooms, living rooms and flats.
When a Desiccant Model Makes Sense
Desiccant models capture moisture in an absorbent material, which is then gently heated to release the water. The same guidance notes that they perform better in cooler or unheated spaces but may use more energy overall. That makes them worth considering for garages or unheated conservatories.
| Type | Best suited to | Main strength | Main limitation |
| Compressor | Heated living spaces | Efficient in warmer rooms | Output falls as rooms get colder |
| Desiccant | Cooler or unheated spaces | Keeps working in cooler conditions | May use more energy overall |
Check the Working Temperature on the Listing
The models in the table list a best working temperature of 5 to 32℃ or 5 to 35℃, for example. If your thermometer readings sit below a model’s stated range for long stretches, that model is unlikely to be the right match for the room.
Size It to Your Space and Moisture Load
Size means daily water extraction, not how big the machine looks.
Litres per Day Is Not Tank Size
A 20L dehumidifier can remove up to 20 litres a day under test conditions, yet its tank might hold only 4 to 6 litres. Most listings rate extraction at 30℃ and 80% relative humidity, so expect less water in a cooler room than the headline figure suggests.
Use the Stated Room Area as Your Starting Point
Treat the stated room areas below as a rough guide, since insulation, heating and ventilation change how each room behaves.
| Daily extraction rating | Stated room area | Tank | Noise |
| 12L | 10 to 25m² | 2L | 38dB (35dB in sleep mode) |
| 16L | 16 to 30m² | 5.5L | 42dB |
| 20L | 20 to 40m² | 6L | 43dB |
Factor In How Your Household Lives
A busy household that dries clothes indoors most days puts more moisture into the air than one person in the same flat, which is a good reason to look further up the capacity range. The HOMCOM 20L Dehumidifier With 6L Tank adds a dryer mode and holds 6L before it needs emptying.
Pick a Drainage Setup You Can Live With
How the water leaves the machine decides how much attention it needs.
Tank Capacity and Auto Shut-Off
The models in the table hold between 2L and 6L. A bigger tank means fewer trips to the sink, and an automatic shut-off stops the unit once the tank is full so it does not overflow.
Continuous Drainage for Hands-Off Running
A drain hose sends water straight into a sink or floor drain, which suits a unit running for long periods in one spot. The HOMCOM 12L Dehumidifier With Drain Hose includes a hose alongside its 2L tank, giving you both options.
| Drainage option | Works well for | Trade-off |
| Water tank | Moving the unit between rooms | Needs emptying, more often in wet weather |
| Continuous drainage | Long running in one spot | Needs a drain within reach of the hose |
Match the Features to Your Routine
Extras earn their place when they solve a real problem.
A Humidistat That Switches Itself Off
A humidistat lets you set a target humidity, pauses the unit once the room reaches it and restarts it when moisture creeps back. A screen that shows the current humidity reading makes it easy to check progress.
Laundry Mode for Indoor Drying
For indoor laundry, a dedicated laundry or dryer mode gives you a setting made for drying clothes nearby. The HOMCOM 16L Dehumidifier With Dryer Mode pairs that mode with a 5.5L tank and a filter system with HEPA, activated carbon and pre-filter layers.
Noise, Weight and Moving It Around
A bedroom unit needs to be quiet enough to live with. The 12L model in the table is rated at 38dB, dropping to 35dB in sleep mode. The units on these listings weigh around 11kg to 12.7kg, so castor wheels and handles matter if you move one between rooms.
Plan for Running Costs and Safe Use
Two final checks help you buy and use the unit well.
Compare Running Costs Between Models
Divide the wattage by 1,000, multiply by the hours of use, then multiply by your unit rate. As an illustrative example at 25p per kWh, a 200W model running for 8 hours costs around 40p, while a 360W model costs around 72p. Find your own rate on your bill or the Ofgem price cap page.
Give It Space and Use It as Intended
The Electrical Safety First guidance advises placing a dehumidifier away from walls, furniture and curtains so air circulates freely, keeping windows and doors closed while it runs and keeping the cable tidy. It also advises against running one overnight or while you are out unless the manufacturer says unattended use is safe.
Quick Checklist Before You Choose a Dehumidifier
- The damp is condensation, not a leak or building fault.
- The type suits how cold the room gets in winter.
- The stated room area covers the space you want to dry.
- The tank size or drain hose suits how often you can empty it.
- The noise rating suits the room it will live in.
- You have compared wattage using your own electricity rate.
Find the Right Dehumidifier for Your Home
With the type, size and features settled, comparing models gets much quicker.
Aosom UK offers a range of HOMCOM dehumidifiers, from compact units for single rooms to larger models with laundry modes and continuous drainage.
FAQs
1. Should I buy a 12L or 20L dehumidifier?
A 12L model often suits a single bedroom or small flat with light condensation. A 20L model gives more headroom for larger spaces, wetter rooms or regular indoor laundry. With a humidistat, the bigger unit can reach your target and pause, so extra capacity does not mean it runs constantly.
2. Is it better to oversize or undersize a dehumidifier?
A slightly larger unit is often the better choice. An undersized unit can run for long periods without bringing humidity down, while a larger one with a humidistat can reach its target sooner and pause. The trade-offs are a bigger footprint, more weight and a higher wattage while it runs.
3. Can a 20L dehumidifier cover a whole house?
It can help in a smaller home if it sits somewhere central, such as a landing, with internal doors open so air moves between rooms. Larger houses, or rooms with heavy condensation, may need a second unit. Check the stated room area on the listing before relying on one machine.
4. Is 70% humidity too high for a house?
Yes, if it stays there. Westmorland and Furness Council advises that indoor humidity should average between 40% and 65%, with kitchens and bathrooms expected to run a little higher, and notes that mould spores multiply at 70% to 80%. A hygrometer helps you check readings room by room.
5. How can you tell if a dehumidifier is good quality?
Look for UKCA or CE safety markings, a fitted UK 3-pin plug and automatic shut-off when the tank is full. Electrical Safety First also advises buying from a reputable retailer or known manufacturer, avoiding second-hand units and registering your appliance so you hear about any recall.