How to Choose The Right Size Dehumidifier

Posted by AlorAir Alex on

Once you have identified the sign of high humidity like:

  • Dampness and musty odors in the house.
  • Mold and mildew growing on items stored in the house.
  • Increased mold and strains on the walls and ceiling.
  • the air in the house feels heavy and High temperatures, which make it difficult to regulate your body temperature.
  • Reoccurring respiratory complications like flu and other allergies.
  • Structure destruction of the foundation especially in the basements and crawl space.

Then you need to buy a dehumidifier!

A dehumidifier regulates the levels of humidity in the air in the house. Dehumidifiers pull the moist air from the house. The air is then directed over coolant-filled coils that condense the moisture. The dry air is then directed out of the dehumidifier back into the house. This process is repeated until the overall level of humidity in the house is at ideal levels.

Some dehumidifiers are fitted with air purifiers that clean the air. They remove any mold spores and bacteria that are in the air.

How to choose the right size of a dehumidifier?

When choosing the right dehumidifier, you should consider the following factors?

  1. Airflow volume of the dehumidifier – you can choose a dehumidifier depending on the amount of air it is able to clean at a period of time.

Dehumidifier measures this in cubic feet per minute (CFM). The recommended CFM is calculated based on the level of humidity in the house and the square footage of the house.

Air changes per hour (ACH) refer to the number of times the air should cycle through the dehumidifier to decrease the level of humidity in the room.

The recommended ACH levels according to the humidity level are:

  • 60 – 70 %( damp air) – This is the normal humidity level in most crawl spaces and basements. The ACH = 3
  • 70-80 %( very damp air) – The room has visible moisture drains on the floor and walls. The ACH = 4
  • 80 – 90% (Wet air) – Visible wet spots on the walls and floor. The ACH = 5
  • 90-100 %( Very wet air) – Puddles of water can be seen clearly on the floor. The ACH = 6

On most dehumidifiers, you find their Air changes per hour (ACH) values clearly indicated.

  1. The area size to be dehumidified – the capacity of any dehumidifier is the amount of moisture (measured in pints) extracted in a span of 24 hours.

This means that smaller capacity dehumidifiers are only ideal to remove moisture in smaller rooms. It is therefore important to ensure you buy a dehumidifier whose capacity is directly correlated to the square feet of the house.

Here is a simple guide from the association of home appliance manufacturers (AHAM) for the recommended dehumidifier’s capacity to house size.


AHAM dehumidifier sizing guidelines: room size versus current humidity conditions

The condition of the basement

500 Sq.

1000 Sq.

1500 Sq.

2000 Sq.

2500 Sq.

Moderately damp room with a musty smell.

10 pints

14 pints

18 pints

22 pints

26 pints

Very moist room with damp stains on the floor and walls.

12 pints

17 pints

22 pints

27 pints

32 pints

Very wet room with clear wet walls and floor.

14 pints

20 pints

26 pints

32 pints

38 pints

Extremely wet room with puddles of water on the floor and dripping water on the walls

16 pints

23 pints

30 pints

37 pints

44 pints


  1. The temperature of the environment the dehumidifier will operate. If the temperatures are low, buy a dehumidifier with de-freezing features. To ensure the dehumidifier is able to keep operating optimally even in temperature as low as 20 degrees.
  2. In internal pump – This is recommended for buyers looking dehumidify the wet large room, where they expect to collect over 20 pints of water. An internal pump directs the water out to a safe place away from the house.
  3. Auto-humidistat – Automatically shuts down the dehumidifier when the humidity levels reach the required levels.
  4. Energy star qualified dehumidifier – This is a dehumidifier that has been proven to consume the least amount of energy needed to operate.

Shop for the best dehumidifiers at the best prices.

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