To test moisture removal rate we placed each dehumidifier in a sealed 50 sq ft room. We then adjusted the humidity in the room to about 92-94% at a temperatures ranging from about 80° F to 85° F. At this temperature and humidity level the dehumidifier was set to high fan speed and its lowest humidistat setting (in most cases this was 35% or 30%) and was then given a “rolling start” to start dehumidifying from the 92-94% level down past 40% relative humidity.
For the first test we started the timer when the dehumidifier achieved a room humidity level of 90% and stopped the timer when it reached 40%. For the second test we started the timer at 80% relative humidity and stopped it at 50% relative humidity. We then repeated this process at least 3 times for each dehumidifier we tested.
Immediately, we saw what could be approximated as a linear relationship between the initial temperature in the room and how long the dehumidifier took to dehumidify from 90% to 40% RH (relative humidity) or from 80% to 50% RH. Thus we plotted points (starting temp vs time taken) and did a linear fit in order to normalize values to a starting temp of exactly 82° F for all units. These were the final values used in our analysis of each dehumidifier’s moisture removal rate – the time taken to dehumidify a 50 sq ft room at 82° F from 90% RH down to 40% RH and from 80% RH down to 50% RH.
Note that at 50 sq ft our test space was very small. We used a smaller sized room for two reasons. First, the smaller size of the room allowed us to adjust the temperature and humidity level in the room to levels simulating a severe humidity problem. We wanted to subject our “test subjects” to the most severe conditions we could manage. It would have been much more difficult to achieve humidity levels as high as 90% or even 80% in a larger sized room. Secondly, because the size of the room was smaller the amount of air that needed to be dehumidified was less, keeping the time taken to dehumidify the room to reasonable levels. For a larger space each test would have taken upwards of several hours. Keeping the test space small allowed us to test each unit multiple times within a reasonable time frame.
Our findings were far from surprising. Larger capacity units removed more moisture more quickly than smaller capacity units. Below is the average time (in minutes) taken to dehumidify the test space for each size class.
Another factor was fan speed. Those units with higher CFM fans performed better. Those units with lower CFM fans performed worse. You’ll notice in the size specific comparison charts below that the Danby and ArcticAire units performed the best in both moisture removal tests. These units had a distinctly greater fan speed than all other dehumidifiers we tested. Of course there were many other factors that played a role in which units dehumidified our test space the most quickly. Dehumidifier capacity and fan speed were simply the most obvious and each of these factors had the most noticeable impact on our results.
Below are our results for all of the dehumidifiers we tested. The heading “90-40%” refers to the time taken (in number of seconds) for the dehumidifier to dehumidify our 50 sq ft test space from 90% relative humidity down to 40% relative humidity. The heading “80-50%” refers to the time taken for the dehumidifier to dehumidify our 50 sq ft test space from 80% relative humidity down to 50% relative humidity.
You can sort the table below by clicking on the up/down arrows next to each column heading. Clicking on the down arrow next to 90-40% moisture removal rate, for example, will sort the dehumidifiers we tested from fastest to slowest for that particular test. Clicking the up arrow will sort the same units from slowest (most time taken) to fastest (least time taken).
70 Pint Dehumidifier Moisture Removal Rates
Manufacturer and Model
50 Pint Dehumidifier Moisture Removal Rates
Manufacturer and Model
30 Pint Dehumidifier Moisture Removal Rates
Manufacturer and Model
#1 The Haier DE65EM, RCA RDH705, and Kenmore KM70 were disqualified from our 70 pint moisture removal tests as they could not reach and/or maintain a humidity level at or below 40%. We discuss these dehumidifiers’ moisture removal test results in more detail in our review for each respective dehumidifier.
#2 All times are in seconds. For example “734″ = 734 seconds taken. We had to put all times in seconds to allow you to sort the tables below.
#3 In the charts above you’re looking for those units with the lowest numbers. A lower time means that the unit achieved the desired humidity level faster.