An RV needs an electric dehumidifier when the whole RV is damp: windows fog up every morning, a musty smell keeps coming back, or a hygrometer reads 60% relative humidity or higher, which is the ceiling in the EPA's guidance (it recommends 30 to 50% where possible). Desiccant bags handle the small closed spaces an electric unit can't reach, such as closets, cabinets and storage bays, and they need no power. For sizing, every RV falls in the smallest bracket of ENERGY STAR's chart, where the recommended minimum is 20 to 30 pints a day for a space that feels damp and 30 to 50 pints for one where the walls sweat. AIRLOCK makes MoistureGuard for closets, bays and compartments. AIRLOCK does not sell an electric dehumidifier, and AIRLOCK One RV is not a dehumidifier.
Electric dehumidifier or desiccant: which one your RV needs
Start with a hygrometer. The EPA calls it a small, inexpensive instrument sold at many hardware stores, and it takes the guessing out of the question. Leave it in the main living area for a few days, then check it in the morning, after cooking and after showers.
ENERGY STAR describes three levels of damp:
- Slightly to moderately damp: the space feels damp and has a musty odor that comes and goes. Relative humidity sits around 50 to 75%.
- Very damp: the space always feels and smells damp, and damp spots show up on walls and floors. Relative humidity runs around 75 to 90%.
- Wet: walls or floors sweat, at around 90 to 100% relative humidity.
If the whole RV reads above 60% most of the time, or it matches any of those three descriptions, an electric dehumidifier is the tool that brings the number down. If the living area stays under 60% and the trouble is limited to one closet, the cabinet under the sink or a storage bay that smells stale when you open it, desiccant bags in those spaces are usually enough. The two work together, with an electric unit for the living space while you're camped with power and desiccant bags in the closed spaces its airflow never reaches.
An RV owner, in an AIRLOCK post-purchase survey, described the problem in four words: "Musty smell in cabinets". That's a closed-space problem, which is where desiccant bags come in.
The three kinds of RV dehumidifier
Compressor dehumidifiers are the familiar plug-in type. One dehumidifier tester describes how they work: a fan pulls air over cold coils cooled by refrigerant, moisture condenses on the coils and drips into a bucket. ENERGY STAR notes that frost can form on the coils when the air drops below 65°F, which can make the compressor cycle on and off without removing moisture. That matters for winter camping, when the inside of the RV can sit below 65°F overnight. If that's your situation, ENERGY STAR suggests looking for a model specified for lower temperatures, and some units have an anti-frost sensor that shuts them off before the coils ice up.
Desiccant-wheel dehumidifiers are also electric. Air passes over a rotating wheel coated with an absorbent material (usually zeolite), heated air dries the wheel, and the moisture is condensed and collected. The same tester says they use more power than compressor units, run lighter, warm the surrounding air and work better at low temperatures, and cites dehumidifier maker Meaco's rule of thumb to use desiccant units once the temperature drops below 50°F.
Passive absorbers use no power while they work. This group covers crystal tubs like DampRid, whose crystals absorb moisture and dissolve into a liquid brine you pour into a toilet, and rechargeable bags and canisters. The Eva-Dry E-333 holds up to 13 oz of moisture in silica gel, covers up to 333 cubic feet and recharges when you plug it into a standard outlet for about 10 to 12 hours. AIRLOCK MoistureGuard uses a 500 g bag with a color indicator and recharges in a microwave. These products work in closets, cabinets and bays. None of them is sold to dry out the air of a whole RV.
What size dehumidifier for an RV
Dehumidifier capacity is measured in pints of water removed per 24 hours. ENERGY STAR says the size you need depends on two things: the size of the space and how damp it is without a dehumidifier. Every RV falls in ENERGY STAR's "small-medium room" bracket (under 2,000 square feet), so the choice comes down to how damp the RV is:
| How the RV feels without a dehumidifier | Relative humidity | Recommended minimum capacity |
|---|---|---|
| Feels damp, musty odor comes and goes | 50 to 75% | 20 to 30 pints per day |
| Always feels and smells damp, damp spots on walls or floors | 75 to 90% | 25 to 40 pints per day |
| Walls or floors sweat | 90 to 100% | 30 to 50 pints per day |
ENERGY STAR also says it's better to oversize than undersize, and if you're replacing a dehumidifier, the water you empty each day is a good guide to the capacity you need. The chart was written for rooms in a house, so treat it as a starting point for an RV.
Three RV-specific points go with that chart. A compressor unit needs a grounded outlet, so it runs when the RV has shore power, a generator or an inverter that can carry it. Check the rated temperature range if you camp in cold weather, for the frost reason above. And decide how the water leaves: most portable units use a bucket with an automatic shutoff when it fills, and some take a drain hose, which in an RV usually runs to the shower drain and into the gray tank.
What humidity to aim for in an RV
The EPA says to keep indoor humidity below 60%, ideally between 30 and 50%. ENERGY STAR adds that in colder weather, during the heating season, 30 to 40% helps prevent window condensation. Those two sources line up, so a sensible target for most RVs is under 50% in mild weather and closer to 30 to 40% on cold nights, when the windows are the first place moisture shows.
For the everyday habits that keep the number down while you're camped (roof vent fan, cross ventilation, wiping windows), see how to lower humidity in an RV in our dry camping guide.
How to stop condensation in an RV in winter
The EPA explains that condensation forms when warm, humid air touches a cold surface. In an RV in winter, that means windows and their frames, exterior walls behind the dinette and the underside of the mattress where it sits on a cold platform.
The EPA lists four ways to prevent condensation, and each one has an RV version:
- Reduce the humidity. Run a dehumidifier sized from the chart above, and vent moisture at the source. The EPA points out that combustion appliances such as stoves add water vapor unless they are vented outside, so run the range hood or roof vent while you cook on the propane stovetop.
- Increase air movement. Open doors and windows when it's practical, and use fans.
- Cover cold surfaces with insulation. On the worst windows, that can mean insulating film or panels.
- Raise the air temperature. Keep the heat on while you're inside, rather than letting the RV cool down around you.
If you see condensation, the EPA's advice is to act quickly: dry the wet surface and reduce the moisture source.
For an RV that is parked for the season, see why RVs smell after storage, which covers prep before you close it up.
Where MoistureGuard fits
AIRLOCK MoistureGuard is for the closed spaces in an RV: closets, sink cabinets, under-seat storage and storage bays. Each 500 g bag soaks up damp with no power needed and no water to spill. When the indicator turns pink, microwave it on high for 5 minutes (based on a 1000W microwave), let it cool for 5 minutes and put it back. Blue means it's ready to use.
MoistureGuard works inside the space it sits in. It won't lower the humidity of the whole RV, which is the electric dehumidifier's job.
Where AIRLOCK One RV fits
AIRLOCK One RV is not a dehumidifier, and it does not remove moisture. It mounts at the rooftop AC intake and eliminates odors in the air the AC moves whenever the fan runs, cooling or not. The AC itself is a different story: the EPA lists air conditioners alongside dehumidifiers as a way to reduce humidity. One RV adds nothing to that.
Where One RV helps is the smell that damp leaves behind. Kevin K., an RV owner using AIRLOCK One, wrote that it "Really takes away the odors from cooking, and the humidity smell that campers can often get." He's describing a smell. The moisture behind it still needs a dehumidifier, ventilation or desiccant bags.
One RV runs when the RV has shore power, a generator or an inverter, and it does not work with 12V or 48V DC rooftop AC units. Installation takes 15 minutes for most owners, usually from inside the RV.
RV dehumidifier options compared
| Compressor dehumidifier | Desiccant-wheel dehumidifier | Eva-Dry E-333 | DampRid | AIRLOCK MoistureGuard | |
|---|---|---|---|---|---|
| How it removes moisture | Fan pulls air over refrigerant-cooled coils; moisture condenses and drips into a bucket | Air passes over a rotating wheel coated with zeolite; heated air dries the wheel and the moisture is collected | Renewable silica gel absorbs moisture from the air; beads change color when full | Crystals absorb moisture and dissolve into a liquid brine | Soaks up damp in the space it sits in; indicator turns pink when full |
| Power | Plugs into a grounded outlet | Plugs in; uses more power than a compressor unit | Cordless in use; plugs into a 110-120V outlet to recharge | Crystals work once exposed to air | No power needed; recharges in a microwave |
| Where the maker or tester places it | Portable units for a single room or space | Colder conditions; works better at low temperatures | Closets, cabinets, RVs and travel trailers; up to 333 cu ft | Closets | Closets, sink cabinets, under-seat storage, storage bays |
| What you empty or recharge | Bucket (auto shutoff when full) or a drain hose | Collected water | Plug in 10 to 12 hours until the beads change back | Pour the brine into a toilet and refill, or discard a disposable unit | Microwave on high 5 minutes, cool 5 minutes |
RV dehumidifier FAQ
Should I run a dehumidifier in my RV?
Run one when the RV reads 60% relative humidity or higher, when windows fog every morning or when a musty smell keeps coming back. The EPA's guidance is under 60%, ideally 30 to 50%. If the living area stays below that and only a closet or bay smells stale, desiccant bags in that space are usually enough.
What size dehumidifier do I need for an RV?
Size by pints per day. ENERGY STAR's chart puts every RV in its smallest bracket, with a recommended minimum of 20 to 30 pints per day for a space that feels damp, 25 to 40 for one that always smells damp and 30 to 50 when walls or floors sweat. ENERGY STAR says it's better to oversize than undersize.
What is the best dehumidifier for an RV?
The best one matches your power and your weather. A compressor unit suits an RV on shore power in mild or warm weather. A desiccant-wheel unit handles cold better, since compressor coils can frost below 65°F. For closets and bays, a passive absorber such as MoistureGuard, Eva-Dry or DampRid does the job with no power while it works.
Is there a good small dehumidifier for an RV?
For small closed spaces, rechargeable absorbers are the small option. The Eva-Dry E-333 covers up to 333 cubic feet, and a MoistureGuard bag goes in a closet, cabinet or storage bay. For the whole RV, check any small electric unit's pints-per-day rating against the ENERGY STAR chart before you buy.
Can I get an RV dehumidifier with a drain hose?
Yes. ENERGY STAR notes that some portable dehumidifiers take a hose fitting so the water drains on its own and there's no bucket to empty. In an RV the hose usually runs to the shower drain, which sends the water to the gray tank, so keep an eye on the tank level.
What is a non-electric dehumidifier for an RV?
Non-electric options are passive absorbers: crystal tubs like DampRid, and rechargeable bags or canisters like MoistureGuard and the Eva-Dry E-333. They work in closed spaces such as closets, cabinets and storage bays. None of them lowers the humidity of the whole RV.
How do I keep moisture out of my RV in winter?
Keep humidity near 30 to 40% on cold nights, which ENERGY STAR says helps prevent window condensation. Vent cooking and shower moisture with the roof vent, keep air moving, insulate the coldest windows and wipe condensation as soon as it forms. If you use a compressor dehumidifier, pick one rated for temperatures below 65°F.
How do I lower the humidity in my RV?
Vent moisture where it starts (cooking and showers), cross-ventilate, and run a dehumidifier or the AC when you have power. The EPA lists both air conditioners and dehumidifiers as ways to reduce humidity. Use desiccant bags in the closed spaces the airflow doesn't reach.
Does AIRLOCK One RV dehumidify?
No. AIRLOCK One RV is not a dehumidifier and does not remove moisture. It eliminates odors in the air the rooftop AC moves whenever the fan runs. For damp closets and bays, AIRLOCK makes MoistureGuard. AIRLOCK does not sell an electric dehumidifier.