Energy Efficiency

How We Tested For Power Usage

To determine each dehumidifier’s energy efficiency we first made sure that the exact same conditions applied to each of our tests. First and foremost we made sure that the relative humidity of the ambient air remained consistent throughout all tests. We set the relative humidity to 50% for the majority of tests because it was easy to do and allowed us to maintain a consistent humidity level throughout the test procedure. It was much harder for us to test at a greater humidity level because the dehumidifier would dehumidify so quickly that it wouldn’t keep the room at a consistent humidity level throughout the duration of the test.

A consistent humidity level was important for the following reason – how much power any particular dehumidifier draws directly correlates with the ambient air’s relative humidity. In the simplest terms, think of the dehumidifier’s internals “working harder” at higher humidity levels. Thus the dehumidifier draws more power at 90% RH (or any other relative humidity percentage greater than 50%) than it does at 50% RH. The Danby DDR050BJPWDB, for example, would draw 760 watts of power at 90% RH and only 572 watts of power at 50% RH. It was therefore of utmost importance that we maintained a steady and consistent room humidity level while testing each dehumidifier for power usage.

Other than keeping the environment consistent throughout each test we also set each unit to high fan speed and waited until the compressor would cycle on prior to measuring power usage. Thus, each unit’s power usage was measured at 50% RH, on high fan speed, and with the compressor cycled on.

Initially, we also tested power usage on low fan speed but soon noticed that the difference between power draw on high and low fan speed was negligible (only a few watts). Thus, we didn’t feel like it was worth our time to test each individual unit for its power usage on the low fan speed setting. Note that we also performed some testing at 90% to 100% RH but had difficulty keeping consistent conditions (as described above) for the tests. In such tests we also saw very little variance in results.

Test Results

Below you’ll find the results of our testing on high fan speed at 50% RH. You can sort the tables below by clicking on the up/down arrows next to each column heading. Clicking on the down arrow will sort the dehumidifiers we tested from most energy efficient to least energy efficient. Clicking on the up arrow will reverse the list from least energy efficient (most energy usage) to most energy efficient (least energy usage).

Note that we’ve also included the manufacturer’s specification for each model’s power usage in the tables below. In earlier years it was always given in watts but more recently it has been specified in amps. Thus, the second column numbers in the first table below – specified in watts – are calculated based on third column numbers – those actually given by the manufacturer – at 115 V.

Important Note – this page now only lists archival test data for discontinued models. Data for current models is now listed in our general buyer’s guide here.

Discontinued 50 Pint (70 pint 2012 DOE) Dehumidifiers

Discontinued 35 Pint (50 pint 2012 DOE) Dehumidifiers

Discontinued 22 Pint (30 pint 2012 DOE) Dehumidifiers

Note: We’ve refined our testing methods over time so the above test results are not 100% comparable to those of the latest models we’ve tested.

The Primary Takeaway

It’s very important that you realize that even though smaller capacity units draw less power per unit time than large capacity units, they will be operating for a much longer time to remove the same amount of moisture.

Here’s what we mean. Let’s say you have a 1000 square foot space that you need to dehumidify. That space contains a set volume of air that is “holding” a set amount of moisture that needs to be removed from the air before the desired humidity level in the space is achieved. Let’s just say it’s “X” pints of moisture in the air. That X pints of moisture (that will eventually drip down into the dehumidifier’s condensate collection bucket) needs to be removed from the air by the dehumidifier. Let’s say, hypothetically, that it takes 24 hours for a 22 pint dehumidifier to remove this set amount (X pints) of moisture from the air within this imaginary 1000 sq ft space.

Our moisture removal tests showed that 50 pint units take about 1/3 (the exact number is 30%) as long as 22 pint units to dehumidify a 50 sq ft space from 90% down to 40% relative humidity. 35 pint units take about half as long as 22 pint units to dehumidify the same space “holding” the same amount of moisture from 90% down to 40% relative humidity.

Now let’s go back to our imaginary scenario of a 1000 square foot space “holding” X pints of moisture which takes a 22 pint dehumidifier 24 hours to dehumidify. By extrapolating our moisture removal test results we can now estimate that a 50 pint unit will take 7.2 hours (30% * 24) and a 35 pint unit will take 12 hours (50% * 24) to fully dehumidify our imaginary 1000 sq ft space.

Now let’s apply what we’ve learned to the real world where you’re going to have to pay a certain amount of money for the energy your dehumidifier uses to do its job and dehumidify the space you need to dehumidify.

Real World Costs Of Dehumidifier Ownership

Your monthly power usage is billed by your utility company by the KWH or kilowatt hour – “kilowatt” refers to power usage and “hour” refers to time. Thus, what matters is not just how much power the appliance draws, but for how long it draws that power.

Let’s apply our imaginary scenario to a real world power bill. We’ll use the national average price for electricity – 12 cents per KWH – in all of our calculations. We’ll use three different sized dehumidifiers to demonstrate our point. Instead of using specific models, we’ll apply average data (average power usage and moisture removal rate for given size class) to three “archetypes”. We’ll also convert watts to kilowatts (371 watts = 0.371 kilowatts, for example) for these calculations to work.

Note: The average values used below were obtained from 2014 data. Since then we’ve tested and reviewed many more dehumidifiers. Rest assured, the average data is still very similar. We just want to note here that the average power draw for dehumidifiers in the 50 pint size class is no longer exactly 612 watts. The average for the 35 pint size class is no longer exactly 454 watts, and so on and so forth.

Dehumidifier 1 >> 22 pint capacity

Power Draw >> 371 watts

Time Taken >> 24 hours

Dehumidifier 2 >> 35 pint capacity

Power Draw >> 454 watts

Time Taken >> 12 hours

Dehumidifier 3 >> 50 pint capacity

Power Draw >> 612 watts

Time Taken >> 7.2 hours

The calculations above speak for themselves. Yes, power draw is greater for larger capacity units. But larger capacity units draw that maximum power for a smaller amount of time. It should now be clear to you that 50 pint dehumidifiers are the most energy efficient. 35 pint dehumidifiers are slightly less efficient. And 22 pint units are the least energy efficient. Thus, we recommend that you stay within the 50 pint size class if energy efficiency is important to you.

As one final nail in the 22 and 35 pint dehumidifiers’ proverbial coffins, consider the fact that the calculations above are only for one hypothetical 24 hour period. If you plan on using your dehumidifier for weeks, months, even years, multiply the above differences in cost by 7, 31, 365, etc. Think about this difference in energy cost when you’re evaluating the retail price differences between 50 pint and 35 pint units or between 50 pint and 22 pint units.

DOE and Energy Star Standards for Energy Efficiency

The findings above – that higher capacity units are a better option if energy efficiency is a priority – are further supported by the latest Department of Energy (DOE) and Energy Star standards for dehumidifiers manufactured since 2019.

The latest DOE standards look like this:

Note how the IEF requirement is less for units with a capacity equal to or less than 25 pints/day.

The latest Energy Star requirements follow a similar pattern:

Note, again, how the IEF requirement is less for units with a capacity equal to or less than 25 pints/day.

The Energy Star requirements outlined here are 21% more stringent for low capacity units and only 13% more stringent for high capacity units compared to DOE requirements. This is due to the fact that new DOE requirements are already fairly stringent compared to previous requirements.

How We Determine Energy Efficiency Scores for Individual Models

In addition to raw power draw, moisture removal rate is also very important in assessing a particular dehumidifier’s overall energy efficiency compared to another model at the same capacity. Why? It’s actually quite simple: Just as a 50 pint dehumidifier can be more energy efficient than a 35 pint dehumidifier because it needs to run for less time than a 35 pint dehumidifier, so also a particular 50 pint dehumidifier can be more energy efficient than another 50 pint dehumidifier because it takes less time to dehumidify a particular space (it has a faster moisture removal rate). It’s really that simple.

We made the mistake in reviews from earlier years of making energy efficiency synonymous with power draw. Thus, 50 pint dehumidifiers (70 pint according to old standards) which tested for lower power draw received higher energy efficiency ratings (scored out of 5) while those dehumidifiers which we tested for higher power draw were rated lower. We didn’t take into account moisture removal rate in evaluating a particular dehumidifier’s energy efficiency.

Rest assured, this mistake was corrected for all ratings and reviews since. We now assess a particular dehumidifier’s moisture removal rate in addition to its power draw in rating its energy efficiency. We suggest that you do the same: evaluate each dehumidifier’s power draw in the tables above IN ADDITION TO each dehumidifier’s moisture removal rate in the tables we made available here.

The Most Energy Efficient Dehumidifiers

Considering everything we’ve discussed so far (tested power draw, tested moisture removal rate, the fact that higher capacity models are generally more energy efficient than lower capacity units, etc.), the three most energy efficient dehumidifiers we’ve tested are:

1. Midea Cube (high moisture removal rate in our testing and low power draw for its size)

2. Frigidaire FFAD5033W1 (second best moisture removal rate among high capacity units tested with average power draw)

3. Black+Decker BDT50WTB (good moisture removal rate and relatively low power draw)