Does a dehumidifier get rid of mold?
No. A dehumidifier does not kill mold and it does not remove it. What it does is take away the condition mold needs to keep growing, by holding the air below roughly 60% relative humidity. That is prevention, and it is genuinely valuable — but if there is already growth on a surface in your house, drying the air will not make it go away. It will still be there, on the same surface, no longer spreading.
We are saying that first because it is the part most pages in this category leave out, and because getting it wrong is expensive in the wrong direction. Someone with real growth who buys a machine and waits has spent money and lost time on a problem that needed physically removing.
What the machine actually does
A refrigerant dehumidifier pulls room air over a cold coil, condenses water out of it, and puts drier air back. Everything it accomplishes follows from that one action:
- It lowers the moisture available at surfaces, which is what stops new growth and stops existing growth expanding.
- It dries materials out slowly — wood, drywall paper and cardboard give moisture back to drier air over days and weeks, which matters for whether damage continues.
- It does nothing to a colony that is already established. Drying does not destroy it. Dormant is not gone, and the material it is growing on is still the material it is growing on.
- It is not an air cleaner. Some units carry a filter, but that filter is there to keep the coil clean. Nothing about condensing water out of air is a filtration process.
So the honest framing is: a dehumidifier is the thing you use so the problem does not come back, and the thing you use to prevent it in the first place. It is not the thing that fixes what is already there.
When the answer is remediation, not a purchase
There is no CTA in this section, because in these situations buying a machine is the wrong next action and we would rather say so.
A visible patch bigger than about ten square feet. The US EPA’s mold remediation guidance uses roughly that area as the point where a homeowner should bring in a professional rather than handle it themselves. Below it, EPA’s own guidance is that many small areas can be cleaned by the householder. Above it, the judgement calls — containment, what gets removed rather than cleaned — stop being obvious. That threshold is a published guideline, not our opinion, and it is worth reading in the original.
Anything that followed a flood, a burst pipe or sewage. Water that has been through a building carries what the building had in it, and porous materials that were soaked — carpet, pad, insulation, drywall below the line — are generally removed rather than dried. A dehumidifier is part of that job, but it is a tool the remediator brings, not a substitute for the job.
Growth inside the HVAC system. If it is in the ducts or on the coil, the system distributes it every time it runs, and a portable unit in one room does not touch it. That is an HVAC contractor’s work.
Growth you can smell but cannot find. A persistent musty smell with no visible source usually means it is behind or under something — inside a wall cavity, under flooring, behind a bath surround. Drying the room air will not reach it, and the only useful next step is finding it, which means someone with a moisture meter and a willingness to open something up.
Anything structural. Soft or spongy wood, sagging subfloor, rot at a rim joist or sill — that is a building question, and a structural engineer or building inspector is the person to answer it. They are also the only people in this list who do not sell you the remedy.
And in every one of those cases, find the water first. Mold indoors is a symptom of a moisture source: a leak, a grading problem, condensation on a cold surface, or air being brought in from somewhere humid. Remediation without fixing the source buys you the same problem again on a delay. That is precisely where a dehumidifier does belong — after the source is fixed and the mess is cleaned up, holding the space dry so it does not recur.
One thing we will not do here is tell you what mold does to you. We are not a health authority and we have no standing to describe symptoms or risk. If anyone in the house is unwell, that is a question for a doctor, and the EPA and your state health department publish material written by people qualified to write it.
The number that suppresses growth
Once you are past the question of whether there is something to clean up, the machine has one job and it is measurable: hold the air below the growth line.
The line is 60% relative humidity, and the working target is 30–50%, aiming at 45%. The reason for the gap is that 60% is a ceiling and not a set point. Indoor humidity moves — with the weather, with cooking and laundry, with how long the air conditioning has been off. If you target the ceiling, you spend part of every humid week above it, and growth responds to the hours spent wet rather than to the weekly average.
Marginal. Technically under the line and with no margin left. One humid week or one power cut puts this above 60%.
Illustrative reading, not a measurement of ours. "Under 60%" is not the same as "at target" — which is the whole reason the band has four bounds instead of one.
The room reading is not the reading that matters
Relative humidity is relative to temperature, and a house is not at one temperature. The hygrometer sits in the middle of the room; the growth happens on the coldest surface, which is a rim joist, an exterior corner, the back of a wardrobe against an outside wall, or a below-grade basement wall. Air that is comfortably under the line in the room can be at saturation against that surface.
Dew point is what connects the two. It is the temperature at which the air becomes saturated, so any surface at or below it is wet — no matter what the room reading says.
| Room reads | Dew point | A 55°F surface |
|---|---|---|
| 45% RH | 47.7°F | Dry — above the dew point |
| 50% RH | 50.5°F | Dry — above the dew point |
| 55% RH | 53.1°F | Dry — above the dew point |
| 60% RH | 55.5°F | Wet — at or below the dew point |
| 65% RH | 57.7°F | Wet — at or below the dew point |
| 70% RH | 59.8°F | Wet — at or below the dew point |
Computed by dewPointF() at 70°F. 55°F is a plausible rim joist or below-grade wall temperature in a heating season — measure yours rather than assuming it.
At the 60% ceiling the dew point is 55.5°F, so a 55°F surface in that room is condensing while the display reads a number nobody would worry about. Pull the room to 45% and the dew point drops to 47.7°F — below that surface, and the surface stays dry. That difference is the whole argument for targeting the middle of the band rather than the ceiling, and it is invisible if you only ever look at the percentage.
How fast it gets there matters more than usual here
For comfort, a dehumidifier that reaches target in three days instead of one is a minor annoyance. For growth suppression it is the whole outcome, because what matters is the time the space spends above the line, not where it eventually settles. Every extra day above 60% is a day of conditions that support growth.
The thing that decides drawdown speed is surplus capacity — how much the machine can remove per day beyond the rate at which moisture is coming back in. A unit barely matched to the steady-state load will hold the number once it gets there, and will take a very long time getting there. A unit with a large surplus spends that surplus on drying the space down.
Below, the steady-state load for a 1,000 sq ft basement with visible beads of moisture on the walls — our arithmetic puts that at 13 pints/day on the modern rating scale — set against four real units from our product data.
| Unit | Tested | Old scale | Surplus | × load |
|---|---|---|---|---|
| Midea 50 pint | 50 | 70 | +37 | 3.8× |
| Waykar 80 pint | 80 | 113 | +67 | 6.2× |
| ALORAIR 113 pint | 113 | 159 | +100 | 8.7× |
| Moiswell 155 pint | 155 | 218 | +142 | 11.9× |
Pints/day are the manufacturers’ tested figures on the post-2019 scale; the old scale column is the same machine as a pre-2019 chart would have labelled it, via newScaleToOld(). Load from sizeFor(). These are catalogue numbers, not measurements of ours.
Two caveats that keep this honest, and they both cut the same way. First, the tested rating is measured at 65°F and 60% RH — in a colder basement, and as the space gets drier, every one of these machines delivers less than its label. The surplus shrinks exactly as you approach target, which is why the last few points of humidity always take the longest. Second, surplus is a ranking, not a schedule: it tells you which unit reaches the band sooner, not how many hours it takes, because that depends on how much water is in the materials, and nobody can read that off a listing.
Size on pints per day, not square feet
The coverage figure on the box is the least useful number in this category. There is no common test behind it, so it is not comparable between brands: in our own corpus, three units all rated 155 pints/day publish 7,500, 6,000 and 6,000 square feet, and a 160-pint unit publishes 2,500. The pints-per-day figure is tested to a standard. The square footage is marketing.
And check which scale a chart is on before you follow it. In 2019 the US Department of Energy moved the dehumidifier test from 80°F to 65°F, so the same machine now earns a number about 30% lower. Every sizing chart written before that change — and most of the ones circulating since, because they were copied from those — is on the old scale, and following one with a modern machine undersizes by roughly a third. Our explainer on the rating change has the detail; the practical version is that a modern “50 pint” removes about what a pre-2019 “70 pint” did.
Waykar Waykar 80 Pints 5000 Sq. Ft 2025 Energy Star Dehumidifier for Basement
80 pints/day tested — 113 on the pre-2019 scale — against a 13 pint/day load, so it has surplus to spend on getting there rather than only holding. It is also the most-reviewed unit in our data, which is a screening signal and nothing more.
$219.98 · 22,300 reviews
The qualification, since we would rather you did not overbuy: if your space is already in the band and you are keeping it there, a smaller unit holds it perfectly well and costs less to run. Surplus buys speed, and speed only matters while you are still above the line.
Continuous, or on a humidistat?
Both, in that order. Run it continuously until the space reaches the band, then put it on a humidistat to hold there. The reasoning falls straight out of the section above: while you are above the line, cycling off wastes the surplus that is doing the work; once you are inside the band, running flat out costs electricity for humidity you did not need to remove.
Set the humidistat at 50%, not 60%. Every humidistat has a dead band — it starts a few points above the set point and stops a few below, so the compressor is not switching every minute. Set it at the growth line and the dead band puts you above the line for part of every cycle. Set it at 50% and the whole cycle stays under.
Continuous mode needs a drain. A machine running continuously into a bucket is a machine that stops when the bucket fills, which on a wet basement can be within hours. A gravity hose to a floor drain is the simple answer; where the drain is higher than the outlet, a condensate pump lifts it. If you are running one in a space you do not visit daily, the drain is not optional — a full bucket is indistinguishable from a working machine right up until you look at the hygrometer.
Watch the temperature. Refrigerant units lose capacity as the space gets colder, and below roughly 60°F many of them ice up and spend their time defrosting rather than removing water. In an unheated basement or garage in winter, that is the point at which a unit specified for low temperatures — or a desiccant machine, which works on a different principle — stops being an upsell and starts being the only thing that works.
And keep measuring where the problem is. The humidistat reads the air at the machine, which is the driest air in the room. A separate hygrometer in the worst corner is the one that tells you whether the set point is actually holding the surface that matters, and the dew point table above is what turns its reading into an answer.
What we can and cannot stand behind
We have never run any of these units, in a basement or anywhere else, and we do not claim to have. Every capacity figure on this page is the manufacturer’s own tested number, every derived figure comes from one shared file of arithmetic you can read, and the review counts are Amazon’s, used as a screening signal rather than as a verdict. Where a number could not be computed honestly, we left it out rather than estimating it.
What we cannot tell you is whether what you have found is mold at all, how far it has gone into the material, or whether it is affecting anyone in the house. Those are questions for a remediator, a building inspector and a doctor respectively — none of whom we are, and all three of whom are worth more than a purchase if you are in that position. Last reviewed 21 August 2026. Damp Down earns a commission on purchases made through links here, which does not change any figure above.
Where this leaves you
Prevention is what this machine is for.
- Hold the space at 30–50% RH. 60% is the growth line, not the target.
- 80 pints/day tested (113 on the pre-2019 scale) against a 13 pint/day load for a 1,000 sq ft wet basement.
- Run continuously to the band, then hold it on a humidistat set at the working ceiling.
- Existing growth still has to be cleaned up or removed — a dehumidifier stops it coming back, it does not undo it.
No first-hand testing claim: we have not run this unit. Price and review count are an Amazon snapshot from the review date above, and capacity figures are the manufacturer's own.
Waykar 80 Pints 5000 Sq. Ft 2025 Energy Star Dehumidifier for Basement
$219.98
3,000+ bought last month