What Size Dehumidifier Do I Need?

The heat during the summer can be cruel, everything is muggy, it is almost impossible to get work done, and unfortunately, fans can only do so much.

The problem with the warmer months is that humidity levels rise, including inside your home. This can lead to heat exhaustion, mould and mildew growth, and an increase in allergies.

But you still need to know, what size dehumidifier do I need?

This simply boils down to knowing the size of the room you need the dehumidifier for in square metres.

How many square metres you need to cover will determine what size unit you will need.

 Below we have all the steps to follow before deciding on the correct sized dehumidifier for your room.


What is a Dehumidifier?

What is a dehumidifier? Well, dehumidifiers work to regulate the humidity in a room by removing any excess moisture from the air, thereby creating a living condition that is inhospitable to dust mites, mould and other allergenic organisms.

Purchasing a dehumidifier can help improve the humidity levels in your house, and create a healthier environment for your family.

What is Dehumidifier Size?

Now that you know about dehumidifiers you are most likely questioning what size unit should be purchased for your home. The size of the dehumidifier is determined by its total moisture removal capacity. Capacity is rated in litres of moisture removed per day during a 24 hour period

A dehumidifier’s capacity indicates how large of a space it will cover in square feet. So, if you already know the square footage of the area, you can get a pretty good idea on what the right size is for your home. 

Below is a chart that will help you determine what size dehumidifier you should purchase.

Conditions in your home 300sq. ft500 sq. ft800 sq. ft1,200 sq. ft
Slightly Damp - 50-60% Humidity

Air feels slightly heavy

Moderately Damp - 60-70% Humidity

Occasional musty smell

Very Damp 70-80% Humidity

Wet spots on walls and floors

Wet - 80-100% Humidity

Mould may be apparent


Size of Room vs. Room Conditions

The first step you should take to determine what capacity dehumidifier you should purchase is to measure the room you need the dehumidifier the most – if you don’t already know its measurements. You can do this by using a tape measure.

Next, ask yourself “how damp is it in here?” Use the chart above to determine which size unit will be useful for the room in question. Other factors can influence the humidity of the room, so when sizing for a dehumidifier, consider these factors.

If your home is in a humid climate, add 5L to the recommended capacity listed in the chart. For areas such as the living room, or a space where multiple people hang out, add 2L. You should also add 2L if the room has multiple windows or doors. If the room is closeby to a washer and drying unit, add 2L. 

Bathrooms harbour more bacteria than almost any other room in the house (the kitchen has the most). You wash your hands, take showers, and flush the toilet, which causes moisture to build up in the air. Because of this, bacteria and mildew builds up. For a bathroom dehumidifier, add 2-5L to your calculation.

dehumidifier chart

Different Types of Dehumidifiers

There are two different types of dehumidifiers: desiccant and refrigerant. Typically, a desiccant dehumidifier has lower capacity ratings and is more efficient in lower temperature climates than refrigerant models. Therefore, it is best to use such units where temperatures fall below 18 degrees celsius. Also, desiccant dehumidifiers are quieter than refrigerant models. 

For very hot and humid temperatures, a refrigerant dehumidifier will best suit your needs. Refrigerant dehumidifiers have a higher capacity rating and are more suited to higher temperatures due to their efficiency.

Heat Pump Dehumidifiers. These dehumidifiers are perfect appliances to put in your attic, basement, and crawl spaces. There are two modes for reducing relative humidity levels. The cooling mode removes humidity through condensation. 

The dry setting causes the heat pump to alternate between heating and cooling modes, allowing the heat pump to maintain a room’s current temperature while also removing excess moisture from the area.

dehumidifier lounge

Steps to Follow to Determine the Size of Your Dehumidifier

Picking a dehumidifier that’s the right size is a lot simpler than you might think, and it only takes three simple steps for you to determine exactly what you need.

Check the Room’s Moisture Level. You will need to measure the level of humidity in the room before you can buy a dehumidifier. You can do this by using a hygrometer to determine how damp the surrounding air is. Ideally, your humidity levels inside should be around 40-50%. 

Anything higher than this and you definitely need a dehumidifier in your home, but if the figures are lower you will need a humidifier. This is because dry air can be just as harmful to your health as damp air. This will also help you determine what size water tank you need. 

Measure the Room’s Size. You can use any current floor plans for your home, or you can take a tape measure and do it yourself. The square footage is fairly easy to determine, and you will need to so that you can choose dehumidifiers that are the right size for your home. 

Compare Room Size vs. Moisture Level for Dehumidifier Size. In order to choose the right size dehumidifier, you will need to combine the measurements from the previous two steps. You can use our handy table at the start of this guide for an accurate look at the water tank capacity you will require, and you should find that it is highly effective at removing moisture from the air.


What size dehumidifier do I need for a garage?

The size of the dehumidifier for your garage really depends on the size of the space in question. A model as small as 15L in capacity can be more than enough for anything up to 1500 square feet. For anything over this, you are better off investing in something with a 25L or 35L capacity.

What size dehumidifier do I need for a 2 bedroom house?

For a house with two bedrooms, you are best picking up a dehumidifier that has a capacity of at least 15L. This is because it is suited for homes up to 1500 square feet, which tends to be more than enough for a standard two-bedroom house.

What size dehumidifier do I need for a 3 bedroom house?

For a house with three bedrooms, you are better off with a dehumidifier that has a capacity between 25L and 35L. These are able to work efficiently in homes above 1500 square feet and all the way up to 2500 square feet.

Is it better to get a bigger dehumidifier?

No, it is not usually better to get a bigger dehumidifier. A model that’s too small for your space will hardly make a dent in the moist air, while one that’s too large may make cause the air to become excessively dry. It is best to pick a model that is suited to the size of your room.

Do I need a dehumidifier in every room?

No, you do not need a dehumidifier in every room. Purchasing multiple dehumidifiers for every room in a house can be costly. If you can afford it go ahead, but usually a dehumidifier is only needed in one or two rooms in your house.

If you have multiple rooms connected by open doorways with a very open floor plan, then the dehumidifier is more likely to be able to work in those other rooms as well. Focus on the rooms with the worst humidity levels (bathroom, kitchen, etc.)

Do dehumidifiers increase your electric bill?

An average unit has a power rating of 280-watts an hour. Suppose your current utility power costs are running at 15 pence per kilowatt-hour. The cost of running a dehumidifier turns out to be 0.280 x 15 = 4.2 pence per hour. So if you were to run your dehumidifier for at least 12 hours a day that would be .50p an hour.

Final Thoughts

Size is everything with dehumidifiers, and it is part of ensuring that the humidity levels in your room remain at recommended levels. Too small, and it will not clear the air of excess moisture efficiently. Too big, and it turns out to be a complete waste of energy that is overcompensating for the space in question. 

If you’re in search of the perfect dehumidifier for your home, why not check out our excellent buyer’s guide? Detailed and packed with superb models to choose from, it could provide you with the best solution for excess humidity.

Last Updated on March 19, 2021 by Gemma Tyler

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