Choosing the right size dehumidifier can make a big difference to how quickly and effectively you control moisture in your home.
A dehumidifier that is too small may need to run constantly and still struggle to reduce humidity. A dehumidifier that is larger than you need may cost more upfront, take up more space and be unnecessary for a small room with light condensation.
The right size depends on the room size, moisture level, temperature, ventilation, how the space is used and whether you are dealing with light condensation, laundry drying, damp smells or a more serious moisture problem.
This guide explains what dehumidifier size means, how litres per day works, what size dehumidifier you may need for different rooms and how to choose the best option for your home or commercial space.
You can also browse our dehumidifiers or read our full dehumidifier buyer’s guide.
What Does Dehumidifier Size Mean?
Dehumidifier size usually refers to how much moisture the unit can remove from the air in a set period, normally shown in litres per day.
For example, a 12 litre dehumidifier can remove up to 12 litres of moisture from the air per day under test conditions. A 20 litre dehumidifier can remove more moisture per day and is usually better suited to larger rooms, heavier damp issues or laundry drying.
This does not mean the water tank is the same size as the daily extraction rate. A dehumidifier may be able to remove 12 litres per day but have a smaller water tank that needs emptying when full.
When comparing dehumidifiers, look at both:
- Extraction rate: How much moisture the unit can remove per day.
- Water tank size: How much water the tank holds before it needs emptying.
The extraction rate tells you how powerful the dehumidifier is. The tank size tells you how often you may need to empty it.
Quick Dehumidifier Size Guide
Use this table as a simple starting point when choosing a dehumidifier for your room or home.
| Room Or Use | Moisture Level | Suggested Dehumidifier Size | Best For |
|---|---|---|---|
| Small bedroom or home office | Light condensation | 10 to 12 litres per day | Everyday moisture control in smaller rooms |
| Bedroom, living room or flat | Regular condensation or musty smells | 12 to 16 litres per day | General home use and damp prevention |
| Medium to large room | Damp air or regular laundry drying | 16 to 20 litres per day | Larger rooms, laundry areas and higher moisture loads |
| Whole flat or small house | Moderate moisture | 20 litres per day or more | Multi-room use when doors are open and airflow is suitable |
| Garage, basement or storage room | Damp or cool conditions | 20 litres per day or specialist model | Moisture control in harder-working spaces |
| Commercial room or large damp space | Heavy moisture | Commercial dehumidifier | Large areas, high moisture loads and business use |
This table is a guide only. The right choice can change depending on how damp the room is, how warm the space is and how often the dehumidifier will be used.
What Size Dehumidifier Do I Need For A Bedroom?
For a small or medium bedroom with light condensation, a 12 litre dehumidifier is often a good starting point.
Bedrooms commonly suffer from condensation because moisture builds up overnight while windows and doors are closed. You may notice water on windows in the morning, damp air, musty smells or black mould forming around window frames and cold corners.
A compact dehumidifier can help reduce excess moisture and make the room feel fresher and drier.
For bedrooms, look for:
- Quiet operation
- Compact size
- Automatic humidity control
- Easy tank emptying
- Timer settings
- Washable filter
If the bedroom is large, poorly ventilated or has heavy condensation, a larger dehumidifier may be more suitable.
What Size Dehumidifier Do I Need For A Living Room?
Living rooms usually need a dehumidifier sized according to room size and moisture level.
If the issue is light condensation or a slightly musty feel, a compact 12 litre unit may be enough. If the room is larger, has poor ventilation, contains lots of soft furnishings or is affected by damp smells, a 20 litre model may be more suitable.
Living rooms can hold moisture in carpets, curtains, sofas and walls, so it can take time for the room to dry out fully. A larger dehumidifier can remove moisture more quickly and may be useful if the room is used heavily.
What Size Dehumidifier Do I Need For A Flat?
Flats can often suffer from condensation because ventilation may be limited and moisture from cooking, showering, drying clothes and breathing builds up indoors.
For a small flat with light moisture issues, a 12 litre dehumidifier may be suitable if it is moved between rooms or used in the main problem area.
For a larger flat, regular laundry drying or more noticeable damp, a 20 litre dehumidifier is usually a stronger choice.
If you want one dehumidifier to help more than one room, place it in a central position and keep internal doors open where appropriate. The unit will work best when air can move freely through the space.
What Size Dehumidifier Do I Need For A House?
For a whole house, dehumidifier size depends on how many rooms are affected and how severe the moisture problem is.
A small domestic dehumidifier can be useful in one problem room, such as a bedroom, utility room or hallway.
If several rooms are affected by condensation or damp smells, you may need a larger dehumidifier, more than one unit, or a better ventilation plan.
A 20 litre dehumidifier is usually more suitable for larger homes, repeated moisture issues and regular laundry drying.
If the whole house has persistent damp, it is important to investigate the cause. A dehumidifier can help control moisture in the air, but it should not be used as a substitute for fixing leaks, penetrating damp, rising damp or serious building defects.
What Size Dehumidifier Do I Need For Drying Laundry?
Drying laundry indoors adds a lot of moisture to the air. This is one of the most common reasons to buy a dehumidifier.
If you regularly dry clothes indoors, choose a dehumidifier with enough extraction capacity and a laundry mode if available.
A 12 litre dehumidifier can be useful for occasional laundry drying in smaller rooms. A 20 litre dehumidifier is usually better if you dry laundry regularly, have a larger drying area or want clothes to dry faster.
For best results, place the dehumidifier in the same room as the laundry, close the door, keep windows closed while it runs and allow air to circulate around the clothes.
What Size Dehumidifier Do I Need For Condensation?
For light condensation on bedroom or living room windows, a 12 litre dehumidifier may be enough.
If condensation appears on several windows, returns quickly after wiping, or is linked with damp smells and mould risk, a larger 20 litre model may be a better choice.
Condensation is usually caused by warm, moist air meeting cold surfaces. A dehumidifier helps by reducing the amount of moisture in the air.
Ventilation also matters. Use extractor fans when cooking or showering, avoid drying laundry in unventilated rooms and keep trickle vents open where fitted.
What Size Dehumidifier Do I Need For Damp And Mould?
If you are dealing with damp smells, visible mould or moisture in walls and furnishings, it is usually better to choose a larger dehumidifier than a very small unit.
A 20 litre dehumidifier can be useful for heavier domestic moisture problems because it removes more moisture per day and is better suited to larger or more demanding areas.
However, it is important to remember that a dehumidifier controls moisture in the air. It does not fix the root cause of damp if the issue is caused by a leak, structural problem, failed damp proofing or water entering the property.
If mould is already present, it should be cleaned safely and the underlying cause should be addressed. The dehumidifier can then help make the conditions less favourable for mould returning.
What Size Dehumidifier Do I Need For A Bathroom?
Bathrooms create a lot of moisture from showers and baths. In most cases, extraction and ventilation should be the first priority.
A dehumidifier can help nearby rooms, hallways or poorly ventilated bathrooms, but it should only be used in accordance with the manufacturer’s safety instructions and kept away from water sources.
If bathroom moisture spreads into bedrooms, landings or hallways, placing a dehumidifier outside the bathroom after showering may help reduce humidity in the surrounding area.
What Size Dehumidifier Do I Need For A Basement, Cellar Or Garage?
Basements, cellars and garages can be more challenging because they may be cooler, less insulated and more prone to persistent damp.
For these spaces, a larger 20 litre dehumidifier or a commercial dehumidifier may be more suitable, depending on the size and severity of the moisture problem.
Temperature matters. Some dehumidifiers perform better in warmer rooms, while cooler spaces may require a model designed for lower temperature operation.
If the area is very damp, used for storage or affected by water ingress, ask for advice before choosing a unit.
What Size Dehumidifier Do I Need For A Commercial Space?
Commercial spaces can need more powerful moisture control than homes.
Shops, offices, storage rooms, warehouses, workshops, gyms, changing rooms and hospitality spaces can all have different humidity problems.
A domestic 12 or 20 litre dehumidifier may be suitable for a smaller office or staff room, but larger commercial spaces often need a commercial dehumidifier with higher extraction capacity and more robust construction.
You can browse our commercial dehumidifiers for larger or more demanding environments.
What Affects The Size Of Dehumidifier You Need?
Room size is important, but it is not the only factor. Two rooms of the same size can need different dehumidifiers depending on the conditions.
Moisture Level
A room with light condensation needs less extraction power than a room with damp smells, mould risk or wet laundry drying regularly.
Room Size
Larger rooms contain more air, which means more moisture may need to be removed. A larger space usually needs a higher capacity dehumidifier.
Temperature
Some dehumidifiers remove moisture more effectively in warmer rooms. Cooler rooms, garages and basements may need more careful product selection.
Ventilation
Poor ventilation allows moisture to build up. A dehumidifier can help, but extraction fans, trickle vents and controlled airflow may also be needed.
Laundry Drying
Drying clothes indoors adds a significant amount of moisture. If laundry drying is a regular use, choose a dehumidifier with a suitable laundry mode and higher extraction capacity.
Number Of People
People add moisture to indoor air through breathing and everyday activity. Bedrooms and busy living spaces can build up humidity quickly.
Building Condition
Cold walls, poor insulation, leaks, damp patches and single glazing can all make moisture issues worse. A dehumidifier helps control humidity, but building problems may still need fixing.
Extraction Rate Vs Tank Size
Extraction rate and tank size are not the same thing.
The extraction rate tells you how much water the dehumidifier can remove from the air in a day under test conditions.
The tank size tells you how much water the unit can hold before it needs emptying.
For example, a dehumidifier may remove up to 20 litres per day, but the water tank may hold much less than that. This is normal. The tank simply needs to be emptied when full, or the unit can sometimes be connected to continuous drainage if the model supports it.
If you want to run a dehumidifier for long periods, look for a larger tank, automatic shut-off and continuous drainage options.
Should You Choose A 12 Litre Or 20 Litre Dehumidifier?
Many customers compare 12 litre and 20 litre dehumidifiers because they are common domestic sizes.
A 12 litre dehumidifier is usually better for smaller rooms, bedrooms, light condensation, occasional laundry drying and general everyday moisture control.
A 20 litre dehumidifier is usually better for larger rooms, stronger condensation, regular laundry drying, damp smells and homes where more moisture needs to be removed each day.
If your room is small and the issue is mild, a 12 litre unit may be enough.
If you want faster moisture removal, have a larger space or regularly dry laundry indoors, a 20 litre unit is usually the stronger choice.
Can A Dehumidifier Be Too Big?
A dehumidifier can be larger than you need, but this is not usually a problem if it has a humidistat and automatic controls.
A larger dehumidifier may remove moisture more quickly, then switch down or off once the target humidity is reached. However, it may cost more upfront, take up more space and be heavier to move.
For small bedrooms and occasional use, a compact unit is usually more practical. For larger rooms and recurring damp, a higher capacity unit is often the better long-term choice.
Can A Dehumidifier Be Too Small?
Yes. A dehumidifier that is too small may run for long periods without reducing humidity enough.
This can happen in large rooms, homes with heavy condensation, laundry drying rooms, damp basements or poorly ventilated spaces.
If the unit is too small, you may notice:
- Humidity remains high
- Condensation keeps returning
- Musty smells do not improve
- Laundry dries slowly
- The tank fills often but the room still feels damp
- The unit appears to run constantly
If moisture problems are persistent, it is usually better to choose a dehumidifier with more capacity.
What Humidity Level Should You Aim For?
Most homes feel more comfortable when humidity is kept within a moderate range.
If humidity is too high, rooms can feel damp, musty and uncomfortable. Condensation and mould risk may also increase.
If humidity is too low, the air can feel dry and uncomfortable.
Many dehumidifiers include a humidistat so you can set a target humidity level. The unit will then switch on and off as needed to help maintain that level.
For more air quality advice, read our air quality buyer’s guide.
Where Should You Place A Dehumidifier?
Place the dehumidifier in the room or area where moisture is most noticeable.
For bedroom condensation, place it in the bedroom or nearby hallway. For laundry drying, place it in the same room as the clothes. For general flat or home use, place it centrally and keep internal doors open where suitable.
For best results:
- Keep the unit on a level surface.
- Allow space around the air inlet and outlet.
- Keep doors and windows managed sensibly while it runs.
- Empty the tank when required.
- Clean the filter regularly.
- Do not place the unit too close to walls, curtains or furniture.
How Long Should You Run A Dehumidifier?
How long you need to run a dehumidifier depends on the moisture level and the room.
For a newly damp room, it may need to run for longer at first. Once humidity is under control, the humidistat can help maintain the room more efficiently.
For laundry drying, run the dehumidifier while clothes are drying and keep the room closed where practical.
For overnight bedroom condensation, you may run it before bed, during the evening or at suitable times depending on noise and comfort.
Always follow the manufacturer’s instructions for safe operation.
Recommended Dehumidifiers
The best dehumidifier depends on the size of the space and the amount of moisture you need to remove.
Best For Smaller Rooms And Everyday Moisture Control: DLUX-12 Dehumidifier
The DLUX-12 Dehumidifier is a compact 12 litre model suited to bedrooms, home offices, smaller living spaces and everyday domestic moisture control.
It is a practical option for light condensation, laundry drying, musty smells and general damp prevention in smaller areas.
The DLUX-12 includes a 2 litre water tank, washable filter, timer, humidistat and portable design with easy-roll wheels.
Best For Larger Rooms And Regular Laundry Drying: DLUX-20 Dehumidifier
The DLUX-20 Dehumidifier is a larger 20 litre model designed for stronger moisture removal in medium to large spaces.
It is a better option if you have heavier condensation, regular laundry drying, larger rooms or more persistent damp smells.
The DLUX-20 includes a larger 6 litre water tank, humidistat, timer, washable filter, child lock and portable design.
Best For Bigger Or More Demanding Spaces: Commercial Dehumidifiers
For large damp rooms, business premises, workshops, storage areas, warehouses or high moisture environments, a domestic dehumidifier may not be enough.
In these situations, browse our commercial dehumidifiers or speak to the CoolEasy team for advice.
Dehumidifier Size FAQs
What size dehumidifier do I need for a bedroom?
For a small or medium bedroom with light condensation, a 12 litre dehumidifier is often a good choice. Larger bedrooms or heavier condensation may need a higher capacity unit.
What size dehumidifier do I need for a 3 bedroom house?
If you are targeting one damp room, choose the size based on that room. If you want to manage moisture across several rooms, a 20 litre unit or more than one dehumidifier may be more suitable.
Is a 12 litre dehumidifier enough?
A 12 litre dehumidifier can be enough for smaller rooms, bedrooms, light condensation and occasional laundry drying. For larger spaces or heavier moisture problems, a 20 litre model may be better.
Is a 20 litre dehumidifier too big?
A 20 litre dehumidifier is not usually too big if you have a larger room, regular laundry drying or recurring condensation. For a very small room with mild moisture, a compact unit may be more practical.
What size dehumidifier do I need for drying clothes?
For occasional laundry drying, a 12 litre model may help. For regular laundry drying or larger loads, a 20 litre dehumidifier is usually a stronger choice.
What size dehumidifier do I need for condensation?
Light condensation in one room may suit a 12 litre unit. Heavy condensation across several windows or rooms may need a 20 litre unit or a wider ventilation and moisture control plan.
Does a bigger dehumidifier use more electricity?
A larger unit may have a higher power input, but it may also remove moisture faster and switch off sooner when the target humidity is reached. Running cost depends on the model, settings, room conditions and how long it runs.
Can one dehumidifier do a whole house?
One dehumidifier can help more than one room if air can circulate freely, but it may not solve moisture issues across an entire house. For whole-home problems, you may need more than one unit, better ventilation or investigation into the cause of damp.
Should I keep windows closed when using a dehumidifier?
Usually, yes. A dehumidifier works best when it is drying the air inside the room. If windows are open, damp outdoor air may keep entering and reduce performance.
Where is the best place to put a dehumidifier?
Put it where moisture is most noticeable, such as a bedroom with condensation, a laundry room or a damp living space. Keep airflow around the unit clear.
Do I need a dehumidifier or an air purifier?
Choose a dehumidifier for damp, condensation, mould risk and laundry drying. Choose an air purifier for dust, pollen, pet dander, allergens and airborne particles.
Do I need a commercial dehumidifier?
You may need a commercial dehumidifier if the space is large, used for business, affected by heavy moisture or needs long-running moisture control.
Final Advice: Match The Dehumidifier To The Moisture Problem
The best size dehumidifier depends on the space and the amount of moisture you need to remove.
For smaller rooms, light condensation and occasional laundry drying, a 12 litre dehumidifier is often a sensible choice.
For larger rooms, regular laundry drying, heavier condensation or more noticeable damp smells, a 20 litre dehumidifier is usually better.
For commercial spaces, garages, storage areas or severe moisture problems, a commercial dehumidifier may be required.
If you are not sure, it is better to ask before buying. Choosing the right size helps improve comfort, reduce moisture more effectively and avoid disappointment.
Explore our dehumidifiers, compare domestic dehumidifiers or speak to the CoolEasy team for help choosing the right size.