The best crawl space dehumidifiers

Who this is for

This guide is for homeowners with a crawl space that smells musty, shows condensation on ducts or joists, reads above 60 percent relative humidity on a hygrometer, or has been flagged by a home inspector or a pest company. It is also for anyone who has just had a crawl space encapsulated and been told to 'add a dehumidifier' without being told which one or why.

We are a water damage restoration crew. We put commercial dehumidifiers under houses to dry them after pipe breaks and groundwater intrusion, and we go back to the crawl spaces that stay wet. The units below are the permanent-install machines we see hold a crawl space at 50 to 55 percent RH year after year, scored against the manufacturers' own published specifications. We did not lab-test them; we tell you what the spec sheets say and what it means on your dirt.

If your crawl space has standing water right now, a dehumidifier is step three, not step one. Pump it out and get air moving first; our 72-hour basement dry-out guide covers the sequence, and if it is sewage, or more than an inch deep across the footprint, call a pro.

The short answer

• Best overall: Santa Fe Compact70. 70 pints/day at 80°F/60%, 2.6 L/kWh, 12 in. tall, 55 lb, MERV-13, 6-year warranty. The height is the reason: it goes where the others do not.
• Best value: AlorAir Sentinel HDi90. 90 pints/day, 2.69 L/kWh, pump included, rated down to 33.8°F, 6-year limited warranty. Taller (17.7 in.) and louder (under 58 dBA), with a MERV-1 filter.
• Upgrade pick: AprilAire E080. 80 pints/day, 2.8 L/kWh, 10-in. duct collars in the box, 45 dBA ducted, optional wall control, built in the USA, 5-year warranty. Needs 15 in. plus clearance.
• Best for small crawl spaces: AlorAir Sentinel HD55. 53 pints/day, 13.3 in. tall, 41.7 lb, 33.8°F rating, 6-year limited warranty. Gravity drain only.
• Also in the table: the Santa Fe Ultra98 (100 pints/day, 320 CFM, the ducted whole-house option) and the AprilAire E100 (the E080's 100-pint sibling; spec sheet still pending our verification).

Every capacity figure on this page is the AHAM rating at 80°F and 60 percent RH. That is not the number printed on a retail portable; the section on AHAM versus DOE ratings below explains the difference, and the sizing calculator converts between them.

The two larger units: Ultra98 and E100

The Santa Fe Ultra98 (100 pints/day at 80°F/60%, 71.4 at 73°F/60%, 320 CFM, MERV-13, 47.5 dBA, 6-year warranty) is the ducted whole-house dehumidifier formerly sold as the Ultra-Aire 98. It belongs on this page because it is the right answer when one machine has to serve a crawl space and the floors above it through ductwork. It is 19.5 in. tall and 81 lb, uses a low-voltage terminal block that requires an external control, and the pump kit is separate. If you are not ducting, it is more machine than a crawl space needs.

The AprilAire E100 is the E080's 100-pint sibling, sold in caster, crawl-space dew-point, Wi-Fi and ventilating variants. We have not yet verified its specification sheet, so its row in the table is deliberately sparse; we publish only numbers we can cite to the manufacturer. For a crawl space over roughly 2,500 to 3,000 sq ft, or a crawl space plus basement combination, it is the one to size against the E080 once the sheet is in hand.

How to choose a crawl space dehumidifier

Capacity: AHAM pints versus DOE pints

Every unit on this page is rated in pints per day at the AHAM condition: 80°F air at 60 percent relative humidity. That is the older standard, and the commercial and crawl space category still uses it. Portable dehumidifiers sold at retail have been rated since 2019 under the Department of Energy test (10 CFR 430, Appendix X1), which runs portables at 65°F/60% and whole-home units at 73°F/60%. Cooler air carries less water, so the same compressor pulls fewer pints: a DOE number is roughly 0.7 times the AHAM number for the same machine.

You can see it in the manufacturers' own sheets. Santa Fe rates the Ultra98 at 100 pints at 80°F/60% and 71.4 pints at 73°F/60%. AprilAire rates the E080 at 80 pints and 65 pints at the same two conditions. ENERGY STAR lists AlorAir's HD55S, the certified variant of the HD55, at 36.33 pints per day at the portable test condition, against the 55-pint AHAM name on the box.

Two consequences. Never compare a crawl space unit's AHAM number to a retail portable's DOE number; a '50-pint' retail box and a '53-pint' AlorAir HD55 are not the same machine. And ignore the 'saturation' numbers some brands put in product names (198 pints for the HDi90, 113 for the HD55); those are measured at 90°F and 90 percent RH, conditions your crawl space will never see. Size on the AHAM figure and the manufacturer's coverage range, then check it in the calculator above.

Low-temperature performance: the spec that matters most under a house

Crawl spaces sit between 45 and 60°F for much of the year across most of the country; ours in the Puget Sound area hold the low 50s from October to May. A refrigerant dehumidifier works by cooling air below its dew point on a coil. The colder the incoming air, the closer that coil is to freezing, and below the manufacturer's minimum the coil ices, the unit defrosts or shuts down, and capacity goes to zero.

The published minimums split the field. AlorAir rates the Sentinel HDi90 and HD55 down to 33.8°F with automatic defrost. Santa Fe rates the Compact70 and Ultra98 at a 49°F minimum inlet air temperature. AprilAire rates the E080 at 50°F for dehumidification with a 40°F dew point floor. In a sealed crawl space in a mild climate the Santa Fe and AprilAire limits rarely bite, because a crawl space below 50°F is usually not generating much moisture. In a cold, leaky or partly vented crawl space, the AlorAir rating is the safer spec, and it is the main reason the HDi90 is our value pick rather than an also-ran.

Watch efficiency as well as capacity. Santa Fe publishes the Compact70 at 2.6 L/kWh at 80°F/60% and 1.96 L/kWh at 65°F/60%; AprilAire publishes the E080 at 2.8 L/kWh at 80°F and 2.35 L/kWh at 73°F. Every compressor unit loses 20 to 30 percent of its efficiency in cool air. Budget your power bill on the cool-air number, not the headline.

Sizing: coverage, sealing and 25 percent headroom

Manufacturers publish coverage in square feet at an assumed crawl space height, usually 5 ft, and the good ones bracket it by how well the space is sealed. Santa Fe's Compact70 page is the honest version: up to 2,600 sq ft tightly sealed, 2,200 moderately sealed, 1,800 loosely sealed. AlorAir says up to 2,600 sq ft for the HDi90 and 1,200 for the HD55. AprilAire's 4,400 sq ft for the E080 is a whole-house figure for a conditioned, sealed structure; do not apply it to a loose crawl space.

Our rule: measure length, width and average height; decide honestly whether the space is tight (encapsulated, vents sealed, rim joist air-sealed), moderate (vapor barrier down, vents closed, some gaps) or loose (vented, or bare soil); take the manufacturer's matching figure; then add 25 percent headroom. A unit sized to run 60 to 70 percent of the time in July lasts longer, holds a tighter humidity band, and still has capacity in reserve the week a supply line lets go. The calculator does the arithmetic and the AHAM-to-DOE conversion.

Height, access and weight

Measure the access hatch, then the lowest clearance between grade and the bottom of the joists along the path to where the unit will sit, and subtract 3 in. for the vapor barrier, a pad and the drain fitting. The Compact70 is 12 in. tall and 55 lb; the HD55 is 13.3 in. and 41.7 lb; the E080 is 15 in. and 63 lb; the HDi90 is 17.7 in. and 70.5 lb; the Ultra98 is 19.5 in. and 81 lb. Over 60 lb is a two-person job through a hatch. Over 15 in. tall needs a crawl space you can move through on hands and knees, not on your stomach.

Ducting a divided crawl space

A free-standing dehumidifier makes its own weather in roughly a 30-ft radius. A long crawl space, one divided by footing walls or a block foundation under an addition, or one with a dead end behind the HVAC plenum needs either two units or one ducted unit: return air pulled from the far end, dry air discharged near the machine. That takes duct collars and a blower with static pressure to spare. The E080 ships with 10-in. collars and holds 135 CFM at 0.2 in. w.c.; the Ultra98 holds 215 CFM at 0.4 in. w.c. and is built for duct. The Compact70 takes an optional duct kit. The HDi90 we link is the non-ductable SKU; AlorAir sells a separate duct-able version. Use rigid duct or hard-elbow flex, keep runs short, and never duct a unit the manufacturer does not rate for external static pressure.

Drainage and condensate pumps

A 70-pint unit makes almost 9 gallons of water a day in July, and where that water goes decides whether the install works. Gravity is best: 3/4-in. or 5/8-in. hose falling continuously, about 1/4 in. per foot, to a floor drain, a sump, or daylight at least 10 ft from the foundation, with no bellies. A hose laid on the vapor barrier sags between the ribs and air-locks; hang it from the joists or run it along the footing.

If the drain is uphill you need a condensate pump. Only the HDi90 in this group includes one. Santa Fe's pump kit for the Compact70 is rated for up to 12 ft of vertical lift. Whatever pump you use should have a check valve and a float safety switch wired to shut the dehumidifier off if the pump fails. Pumps are the most common failure point we see under houses, and a failed pump dumps 9 gallons a day onto the vapor barrier until someone notices. Set the unit in a drain pan with a water alarm. Never drain onto the soil under the house.

Seal the crawl space first

This is the step that gets skipped, and it is why most crawl space dehumidifiers 'do not work'. A vented crawl space in a humid climate pulls outside air through the vents all summer; at 85°F and 70 percent RH that air carries more water than any unit here can remove, so the machine runs continuously and loses. The sequence is: fix bulk water (grading, downspout extensions, an interior drain and sump if the water table demands it); lay and seal a vapor barrier over the soil and up the walls (6-mil is the code minimum in most jurisdictions, 10- to 20-mil reinforced is what lasts); seal the vents; air-seal and insulate the rim joist; then dehumidify. Expect a freshly sealed crawl space to work the dehumidifier hard for two to four weeks while the soil and framing give up stored moisture, then settle into cycling.

Target 50 to 55 percent RH, and framing under 16 percent moisture content on a pin meter. Sustained readings above about 20 percent support mold growth and, over time, decay fungi. If the framing already reads above 20 percent or you can see growth on the joists, that is remediation, not dehumidification; start with our emergency page or get a quote for encapsulation and remediation below.

Electrical and GFCI

These units draw 5 to 6 A running on 115 V (5.1 A for the Compact70 and E080, 5.56 A for the HDi90, 5.6 A for the Ultra98), plus a condensate pump if you add one, and more at compressor start. Give the dehumidifier its own 15- or 20-A circuit if at all possible; sharing a circuit with the sump pump is how both end up off during the storm. Crawl space receptacles must be GFCI-protected under the National Electrical Code, and compressors can nuisance-trip older GFCIs; if yours trips, have an electrician fit a current-generation GFCI breaker rather than defeating protection. AprilAire sells a hardwired E080H for installs where a cord and receptacle are not wanted. Measure cord reach before you pick the spot; an extension cord under a house is a code violation and a fire risk.

Filters, controls and service

Filter ratings: MERV-13 (Santa Fe Compact70 and Ultra98) catches fine dust and mold spores; MERV 8 (AprilAire E080) catches dust; MERV-1 (AlorAir standard) is a coil guard. A higher MERV means checking the filter every three to six months in a crawl space, because a loaded filter cuts airflow and capacity. Controls: the Compact70 and HD55 are set at the unit; the HDi90 has an optional remote; the E080 takes AprilAire's Model 76 wall control; the Ultra98 requires an external control. A wall control or a Wi-Fi hygrometer parked in the far corner of the crawl space costs little and means you will actually know when the unit stops. Service: vacuum the coil and flush the drain line every spring.

What we skipped and why

Retail 50-pint portables. They are rated at 65°F/60%, carry a 41°F operating floor, have buckets, and are not designed to run unattended on dirt for years. Their coverage claims assume a sealed room. If you are tempted because of price, buy the AlorAir HD55 instead; it is built for the job.

Desiccant dehumidifiers. They work below 50°F where compressors stall, but they use two to three times the electricity per pint and most residential models are small. They are a niche answer for cold, unsealed crawl spaces that should be sealed instead.

Santa Fe Advance90. A long-time favorite, but it no longer appears on Santa Fe's product lineup, which now shows an Advance Dry110 in its place. We have not verified the new unit's sheet yet and will add it when we have.

AlorAir HD55S, HDi65S and the duct-able HDi90, Abestorm Hurricane 85, AprilAire E130. Either variants of units already here or models we have not finished documenting against manufacturer sources. We add products when we can cite the spec sheet, not before.

Anything we could only verify from retailer listings. Our rule is manufacturer documentation or nothing. That is also why two cells in the table above are empty rather than filled with a number copied from a product listing.