A dehumidifier removes water vapor from air. Warm moist air is drawn across a cold surface or a moisture-absorbing material, the water comes out of the air, and drier air goes back into the room.
That simple description covers two very different products. A household dehumidifier keeps a damp basement comfortable. A commercial low grain refrigerant unit dries the structure of a building after a water loss, pulling moisture back out of framing and subfloor. They look similar, they are rated in the same units, and they are not interchangeable. This page covers how they work, how the two classes differ, how to size one, what they cost, and the specific role drying plays during mold remediation.
Prices on this page are ranges checked in September 2026 and will drift. Treat them as a planning figure, not a quote.
Two technologies, and which one suits a job depends mostly on temperature and how dry you need to get.
Refrigerant, also called condensate. A fan pulls air across a cold evaporator coil. Water condenses out onto the coil, drains away, and the air is reheated slightly before it leaves. This is what almost every household unit is, and what most restoration units are. It works well in warm, humid conditions and loses efficiency as the air gets colder and drier.
Low grain refrigerant, or LGR. The same principle with an added pre-cooling stage. Incoming air is cooled by outgoing air before it reaches the coil, so the coil sees air that is already colder and can pull it down much further. This is what lets an LGR unit keep working in conditions where a standard refrigerant unit has effectively stopped.
Desiccant. No coil. Air passes over a moisture-absorbing material, usually a silica gel wheel, which is then heated to drive off the collected water and vented away. Desiccants keep working at low temperatures and very low humidity where refrigerant units stall, which makes them the choice for cold spaces, deep drying, and materials like hardwood and plaster that release moisture slowly.
Capacity gets all the attention. The number that actually predicts drying performance is grain depression, the difference between the moisture content of the air going in and the air coming out, measured in grains of water per pound of air.
A household unit might achieve 30 to 40 grains of depression. A good LGR achieves 60 or more. That difference is what determines whether a unit can pull moisture out of wet framing or only make a room feel less clammy, and consumer listings essentially never mention it.
This is the comparison most people actually need, so it is worth doing properly.
| Household unit | Commercial LGR | |
|---|---|---|
| Typical capacity | 20 to 50 pints per day | 130 to 240 pints per day |
| Effective range | Down to roughly 40% RH | Down to 20 to 30% RH |
| Grain depression | 30 to 40 | 60 or more |
| Drainage | Bucket, or gravity hose | Continuous pump, lifts to a sink or window |
| Duty cycle | Intermittent, cycles on and off | Built to run 24 hours a day for weeks |
| Ducting | None | Often ducted to direct dry air into cavities |
| Build | Plastic housing, light | Roto-molded case, stackable, made to be dragged |
| Price | $150 to $400 | $979 to $4,415 depending on class |
Why the difference matters. A household dehumidifier is designed to make an already-dry building comfortable. It is rated at comfort conditions, roughly 80 degrees and 60% relative humidity, and its performance falls off sharply below about 40% RH. That is fine, because nobody wants a basement at 25% RH.
Structural drying is a different task. You are not trying to make a room feel better, you are trying to pull water back out of framing lumber, subfloor and sheathing that absorbed it. That requires holding the air well below the moisture content of the wet material for days, and it requires staying effective as the air gets drier and drier. Below 40% RH is exactly where the work happens, and it is exactly where a household unit gives up. LGR technology typically removes moisture 40 to 60% faster through that final drying phase.
Two dehumidifiers can be advertised at wildly different pint numbers and perform identically, because manufacturers quote different things.
Saturation figures can run more than double the AHAM figure for the same machine. So a "200 pint" dehumidifier and a "130 pint" dehumidifier may be the same class of equipment, with one quoted at saturation and one at AHAM.
Compare AHAM to AHAM. If a listing gives only one number and does not say which it is, assume saturation and mentally halve it. This one habit will save you from buying an undersized machine.
Note the word during. Drying is not a step that happens after the project, it runs through the middle of it, and treating it as a finishing touch is one of the most common ways a competent remediation still fails.
Three things make a remediation work area wetter than people expect:
So dehumidifiers run alongside the air scrubbers, usually paired with air movers that accelerate evaporation off wet surfaces so the dehumidifier has something to capture.
"It feels dry" is not a standard. Proper drying is measured.
The method is to find an unaffected reference area, meaning the same material in the same building that was never wet, and measure its moisture content with a moisture meter. That reading is the target. The affected material is dried until it reaches that number, not until a calendar day arrives or the equipment is needed elsewhere.
Readings are taken and logged daily, at the same points, so there is a record of the structure drying rather than a claim that it did. That log is part of what an insurer, a buyer's inspector or an attorney will eventually ask for.
Of all the ways a mold remediation goes wrong, this is the most common and the most expensive. The growth is removed correctly, the cleaning is done properly, the containment was built well, and then the walls are closed before the framing reached its dry standard. Within weeks there is growth again, this time behind brand new drywall where nobody will see it until the next inspection.
Reconstruction waits for documented dry readings. That is the whole rule.
Read more: the mold remediation process · Read more: air scrubbers and negative air machines · Read more: clearance testing explained
For household use, size by area and how damp the space is. A rough guide for typical 8 foot ceilings:
| Space | Slightly damp | Very damp or wet |
|---|---|---|
| 500 sq ft | 20 to 30 pints | 30 to 40 pints |
| 1,000 sq ft | 30 to 40 pints | 45 to 50 pints |
| 1,500 sq ft | 40 to 50 pints | 50 to 60 pints |
| 2,500 sq ft | 50 to 60 pints | 60 to 70 pints or two units |
"Slightly damp" means it smells musty in humid weather. "Very damp or wet" means visible condensation, damp walls, or standing water at some point in the year.
For structural drying, sizing works from the water load rather than the floor area: how much water went into the building, how much material is wet, how deeply it penetrated, and how fast the job needs to finish. That calculation belongs to the restoration contractor, and it is one of the things a written protocol should specify rather than leave to whatever equipment happens to be on the truck.
One counterintuitive point. An undersized unit running constantly is a worse outcome than a correctly sized one cycling. It costs more to run, never reaches the target, and creates the impression that drying is happening when it is not.
Household units are almost always worth buying. They are inexpensive, the need is usually seasonal and recurring, and rental rates make no sense for months of use.
Commercial LGR units are usually worth renting for a one-time event. Home Depot and general rental yards carry restoration-grade equipment, including Dri-Eaz units in the 29 gallon per day class. If you own rental property, manage a portfolio, or work in construction, owning changes the math.
| Class | AHAM capacity | Price |
|---|---|---|
| AlorAir Storm Pro | 190 pints/day | about $979 |
| AlorAir Storm Elite | 232 pints/day | about $1,699 |
| Dri-Eaz LGR 3500i | 150 pints/day | about $4,415 |
| Dri-Eaz LGR 7000XLi | 29 gallons/day class | professional tier |
| Phoenix LGR range | varies | the main alternative to Dri-Eaz |
The gap between the AlorAir tier and the Dri-Eaz tier is mostly durability, serviceability and resale. For occasional use the less expensive machines are genuinely capable. For daily commercial work, the professional units survive being dragged in and out of buildings for a decade and hold their value.
The cost nobody includes in the comparison is electricity, and on a restoration unit it is not small.
A commercial LGR draws roughly 8 to 12 amps at 115 volts, which is on the order of 1,000 to 1,400 watts. Running one continuously for a week is roughly 170 to 235 kilowatt-hours. At average US residential rates that is meaningful money, and running three of them plus air movers on a whole-house dry-out is a noticeable spike on a power bill. It is also why a structural dry-out often needs circuits planned rather than everything plugged into one outlet.
Other ongoing costs are modest: air filters, periodic coil cleaning, and pump maintenance on units with a condensate pump. Keep the coil and filter clean, because a dirty coil cuts capacity substantially while the machine appears to be working normally.
Yes for humidity control. Buying a dehumidifier for a damp basement, sizing it properly, draining it continuously and keeping the space between 30 and 50% RH is straightforward, effective, and one of the best preventive measures available to a homeowner.
Yes, with care, for a small spill caught immediately. A contained water event on a hard surface, dried promptly with a fan and a dehumidifier, does not need a contractor.
No for structural drying after a real water loss. The target there is a documented moisture content inside framing and subfloor, verified against an unaffected reference area, not a room that feels dry. Getting that wrong is invisible at the time and expensive later, because the wall gets closed and the problem starts again out of sight.
Read more: what a moisture meter actually tells you · Read more: air movers and how they pair with dehumidification
Yes. Restoration-grade units are widely available to rent and straightforward to operate. The judgment that is hard is not running the machine, it is knowing when the structure is actually dry, which requires a moisture meter and an unaffected reference area to compare against.
Restoration-grade units are available by the day, week or month at general rental yards and home improvement stores. Because household units cost only $150 to $400 to buy outright, renting rarely makes sense at the consumer end and usually does make sense for a one-time commercial dry-out.
Roughly $979 for an AlorAir Storm Pro at 190 pints per day AHAM, about $1,699 for a Storm Elite at 232 pints, and about $4,415 for a Dri-Eaz LGR 3500i at 150 pints. The premium on the professional tier buys durability, serviceability and resale value rather than raw capacity.
A low grain refrigerant unit pre-cools incoming air before it reaches the coil, so it keeps removing moisture down to 20 to 30% relative humidity. A standard refrigerant unit loses efficiency sharply below about 40% RH. That range below 40% is exactly where structural drying happens, which is why LGR units are standard on restoration work.
For household use, roughly 30 to 40 pints for a 1,000 square foot damp space, and 45 to 50 pints if it is very damp. Compare AHAM ratings rather than saturation ratings, because saturation figures can be more than double for the same machine. For structural drying, sizing is calculated from the water load rather than floor area.
Keep indoor relative humidity below 60%, and ideally between 30 and 50%. Mold needs moisture, and sustained humidity above 60% is enough for growth on ordinary building materials and contents without any leak involved.
Until the affected materials reach the moisture content of an unaffected reference area of the same material in the same building, verified with a moisture meter and logged daily. That is typically several days to a couple of weeks. Running to a calendar date rather than to a measured target is how buildings get closed up wet.
No. A dehumidifier removes the moisture mold needs to grow, which stops growth from spreading and prevents new growth. It does not remove or kill existing growth, which has to be taken off surfaces mechanically. Drying is an essential part of remediation, not a substitute for it.
A commercial LGR draws roughly 1,000 to 1,400 watts, which is around 170 to 235 kilowatt-hours over a week of continuous running. Household units draw far less but still run for long periods. On a multi-unit structural dry-out, circuit capacity needs to be planned rather than assumed.
MI&T is an inspection and testing company. We do not perform remediation or structural drying, and we do not sell equipment.
Where we come in is establishing whether there is a mold problem and how far it extends, and afterward verifying that the work succeeded, which includes confirming that the structure actually reached a dry standard before anyone closed it up. A contractor's assurance that a building is dry is not the same as a documented reading from someone with no stake in the answer.
Find your nearest MI&T location to schedule an inspection or clearance test.
