What Size Dehumidifier Do I Need? Pints per Day, AHAM vs Saturation and a Sizing Chart

How we made this guide: picks, prices and specs come from our catalog and the makers' published specs, owner quotes come from customer reviews on our product pages and every guide is checked and edited by Trevor Hall.

For a 1,000 sq ft basement that always feels and smells damp, with damp spots on the walls or floor, ENERGY STAR's dehumidifier page points to 25 to 40 pints per day, and the AlorAir Sentinel HD90 at $1,047.11 clears that range with room to spare. If the space only feels damp now and then, the page's range is 20 to 30 pints. The AlorAir Sentinel HS35 at $449.66, rated at 35 pints per day at AHAM conditions, is the smallest machine here that reaches it.

The worked example: a 1,000 sq ft damp basement

ENERGY STAR's dehumidifier page groups spaces by how damp they are without a dehumidifier and by size, under 2,000 sq ft or over. A 1,000 sq ft basement falls in the under-2,000 column. If it consistently feels and smells damp and damp spots show on the walls or floor, that is "very damp" on the page, which it ties to 75 to 90% relative humidity. The page lists 25 to 40 pints per day for that case.

Now match a machine. The HS35 is rated at 35 pints per day at AHAM conditions, so it falls short of the 40 pint top of the range. The HD90 is rated at 90 pints per day at AHAM conditions, and AlorAir also lists it at 47.71 pints per day "at DOE (60F, 60% RH)". Even on that colder, tougher test point, the figure is above 40. AlorAir lists the HD90 for spaces up to 2,600 sq ft and the HS35 for spaces up to 1,000 sq ft, and coverage claims are each maker's own, so treat them as a cross-check and not the main rule.

The ENERGY STAR page does not say which test point its ranges use, and it adds that it is better to oversize than undersize. That is why this guide leans toward the larger machine when a space sits between two rows.

If the same basement is only slightly to moderately damp, drop to the 20 to 30 pint row. The HS35 reaches it on its 35 pint AHAM rating. But ENERGY STAR's conversion table puts an old-test 30 pint unit at about 20 pints and a 40 pint unit at about 25 on today's DOE test. If the page's ranges are read in DOE pints, the HS35 sits at the bottom of the row (our reading of that table). Treat it as the minimum, and choose the HD90 if the space is close to 1,000 sq ft or runs cool.

The sizing chart: pints per day by area and dampness

This table is the ENERGY STAR dehumidifier page's capacity guidance, with our reading of which machines in our range fit each row. The machine column uses AHAM ratings only, and only for machines whose AHAM figure reaches the top of the range. This is our calculation from the page's ranges and the makers' ratings, not a maker's sizing promise.

Read the last column with two cautions. First, the page's top rows end in "or more" for big spaces, so 50 pints is a floor there, not a target. Second, the page does not state its test conditions, so compare its numbers with the AHAM or DOE lines on a spec sheet only as a rough guide and size up when unsure.

AHAM, saturation and DOE: why one machine has three numbers

A pints-per-day rating is only meaningful with its test condition. The same machine removes more water in warm, wet air than in cool, drier air, so makers can print several figures. Here is how the six machines in this guide are rated, exactly as the maker or our listing states it.

Two rules keep you out of trouble. Never compare an AHAM figure from one machine with a saturation figure from another: a "198 pint" box number and a "90 pint" box number can describe the same HD90. And treat the Ebac DD400-P's 71.5 pints as its own figure, because Ebac's listing gives no test condition and a desiccant wheel behaves differently from a refrigerant coil anyway. For how each type removes water, see how a dehumidifier works.

The DOE test point in plain terms

ENERGY STAR explains that since June 2019 the Department of Energy's test rates portable dehumidifiers at 65F rather than the old 80F, so a new model shows a smaller capacity number than an older one of the same size. Its approximate conversion table puts an old 30 pint portable at about 20 pints on the new test, an old 50 at about 30, an old 70 at 40 to 45 and an old 90 at about 55. AlorAir lists the HD90 at 47.71 pints per day "at DOE (60F, 60% RH)", about half its 90 pint AHAM rating. So check which test each number comes from before you compare two labels: a 40 to 45 pint unit on the DOE test can be the same size of machine as a 70 pint unit rated the old way. That drop is also why a cool basement needs more capacity than the AHAM figure suggests.

How to measure your space

1. Measure floor area, length times width, in square feet. For an L-shape, split it into rectangles and add them.
2. Note the ceiling height. The page's ranges work in floor area, and a tall space holds more air than a standard one, so aim for the top of the range or the next column if the ceiling is well above 8 ft.
3. Judge dampness honestly. A damp feel and a musty smell that come and go point to slightly to moderately damp. A space that always feels and smells damp, with damp spots on walls or floor, is very damp. Sweating walls or floor, seepage or laundry drying in the space point to wet. A hygrometer reading over a few days is better than a guess.
4. Check the coldest temperature the space reaches. Compare it with the machine's operating range: the HS35 lists 33F to 105F, the HD90 33.8F to 104F and the Storm Elite 33.8F to 105F.
5. Plan the drain. Gravity-drain units need a hose that runs downhill to a floor drain, sump or outside. If the water has to go up, you need a pump.
6. Pick the row in the chart, then pick a machine whose AHAM rating reaches the top of that row.

The humidity setpoint matters too. The listings give the HS35 fixed settings of 30%, 50% and 70% RH, the HD90 a range of 36% to 90% and the Storm Elite 25% to 80%. If you are drying a crawl space, the same steps apply and crawl space dehumidifier installation covers placement and drain lines. For basements that have already grown mold, basement mold remediation explains the humidity to hold afterward.

What changes the answer

Temperature

Cool spaces make a refrigerant dehumidifier work harder for the same pints, and every machine in this guide has a lowest operating temperature. The refrigerant models here list a floor of 33F to 33.8F. Below that, the HS35 and its siblings are the wrong tool, and a desiccant unit like the Ebac DD400-P is the one to look at. Ebac's brochure for the DD400-P lists a minimum operating temperature of -4F (-20C) and a maximum of 104F (40C).

Moisture source

A dehumidifier manages humidity. It does not fix a leak, a missing vapor barrier or a gutter that dumps water against the wall. If a space keeps refilling, find the source first. Venting a crawl space covers why open vents often make a damp space worse in humid weather.

One large machine or two smaller ones

One machine is simpler to run and drain. Two smaller units can serve two rooms that a single hose cannot reach, and they spread the electrical load. A divided basement with a closed-off utility room is a typical case for two. For a single open space, one correctly sized unit is the plain choice.

Drain and power

Check the amps before you plug in. The HS35 draws 2.9 A on 115 V, the HD90 5.56 A, the Storm Elite 9.0 A and the XD-165L 10.2 A. The CD425-D lists a maximum of 16 A on 220 to 240 V single-phase and also comes in a 440 to 460 V three-phase version. The listings also give efficiency: 2.0 L/kWh for the HS35, 2.69 L/kWh for the HD90 and 2.4 L/kWh for the Storm Elite. More liters per kWh means less power for the same water. To estimate running cost from watts and hours, see how much it costs to run a dehumidifier.

Machines that fit each size

These are the six machines we carry that map to the rows above. Each coverage figure is the maker's claim and not a measurement. Makers rate it differently.

Small damp space: AlorAir Sentinel HS35

The HS35 is the smallest machine in this guide. It lists 35 pints per day at AHAM conditions and 70 at saturation, weighs 37.8 lb and draws 2.9 A. Humidity is set by a knob with fixed 30%, 50% and 70% RH settings plus continuous mode. It drains by gravity only, through a 6.5 ft hose, so the water must run downhill.

Skip it if the space is over about 1,000 sq ft or is very damp or wet. Skip it too if the drain sits uphill from the machine.

Large basement or crawl space: AlorAir Sentinel HD90

The HD90 is the answer for most 1,000 to 2,600 sq ft damp basements and crawl spaces. It lists 90 pints per day at AHAM, 198 at saturation and 47.71 at DOE (60F, 60% RH), pulls 210 CFM on 5.56 A, and AlorAir lists it for up to 2,600 sq ft. It weighs 67.2 lb, has a 6 inch supply duct adapter as standard and drains by gravity, with terminals for an optional external condensate pump. Browse the whole crawl space dehumidifier group if you want to compare siblings.

Skip it if the space is small and only moderately damp. A 35 pint machine will do the job for less money.

Water-damage and large spaces: AlorAir Storm Elite

The Storm Elite lists 125 pints per day at AHAM and 270 at saturation, moving 300 CFM on 9.0 A. AlorAir rates it for spaces up to 3,000 sq ft. A built-in condensate pump lifts water up to 15 ft, and the 12 inch inlet and supply allow a 20 ft total duct run. At 103 lb it is wheeled, not carried. It is the one to size up to when a space is over 2,000 sq ft and wet.

Skip it if you only have a 15 A circuit shared with other equipment, since 9.0 A leaves less room than a small unit, or if the space is under about 1,500 sq ft where the HD90 is plenty.

Restoration and big loss: XPOWER XD-165L LGR

The XD-165L is an LGR (low grain refrigerant) machine built for restoration work. XPOWER lists 165 pints per day at AHAM and 280 at saturation, 476 CFM, 10.2 A on 115 V and a 25 ft power cord. An automatic purge pump sends water through a 40 ft hose, and two units can stack. It weighs 121.3 lb. For a wider selection, see the flood restoration dehumidifiers.

Skip it if the job is a normal damp basement. It is more machine, power and weight than the space needs.

Cold spaces: Ebac DD400-P desiccant

The DD400-P is a desiccant unit, not a refrigerant one. It lists 71.5 pints per day, with no test condition stated, 197 CFM, 1,800 W maximum, 220 to 240 V and a 10 ft power cord. At 68 lb on wheels it moves easily. Its draw is the reason to check your outlet before ordering: 220 to 240 V is not a standard wall outlet. See also our Ebac dehumidifiers.

Skip it if the space stays above about 65F, the point below which ENERGY STAR warns refrigerant coils can frost. There a refrigerant unit such as the HD90 does the job at a fraction of the price.

Warehouse and industrial: Ebac CD425-D

The CD425-D is the largest machine here. Ebac lists 285 pints at AHAM conditions and up to 50 gallons per day with no condition given, 1,750 CFM and a suggested room size of 10,000 sq ft. Power is 220 to 240 V single-phase (16 A maximum) or 440 to 460 V three-phase, with or without a pump. The lowest operating temperature is 33F and it weighs 353 lb. The 220 V single-phase version without a pump is $10,676.

Skip it for homes and small commercial rooms. It is built for warehouses, factories and large facilities.

Cold spaces and desiccant: when to change type

ENERGY STAR notes that frost can form on a refrigerant unit's coils below 65F, and suggests a unit specified for lower temperatures when a space usually sits below that. The refrigerant machines here list operating floors of 33F to 33.8F, so they keep running in a cool basement, but at a lower output. The HD90's 47.71 pints at what AlorAir labels the DOE point, against 90 pints at AHAM, shows how large that drop can be. If the space regularly drops toward freezing, such as an unheated garage or a winter job site, a desiccant unit is the type built for it. If it sits in the 50s, size a refrigerant unit one row up or look at a desiccant.

Sizing for water damage and large losses

Drying a wet building after a leak or flood is a different job from holding a damp basement dry. Restoration crews size to the volume of air and the class of water, and IICRC publishes initial dehumidification factors for it. For refrigerant units the formula is cubic feet divided by a chart factor, which gives total pints per day, then divided by the dehumidifier's AHAM rating, which gives the number of units. The LGR factors are 100 for Class 1, 50 for Class 2 and 40 for Classes 3 and 4. Conventional refrigerant units use 100, 40 and 30 for Classes 1 to 3. The formula uses the AHAM rating, not the saturation figure.

A worked example, our calculation: a 1,000 sq ft basement with an 8 ft ceiling holds 8,000 cubic feet. As a Class 2 loss with LGR units, 8,000 divided by 50 is 160 pints per day. The XD-165L is rated at 165 pints at AHAM, so one unit covers it. As a Class 3 loss, 8,000 divided by 40 is 200 pints per day, which means two XD-165L units. For desiccants IICRC works in air changes per hour instead: cubic feet x ACH divided by 60 gives the CFM needed. At 2 ACH for Class 2, 8,000 x 2 divided by 60 is about 267 CFM, or two DD400-P units at 197 CFM each. IICRC calls these initial recommendations, so treat them as starting numbers.

The same arithmetic for other floor areas, with an 8 ft ceiling and XD-165L units at 165 pints AHAM:

This is our calculation from IICRC's initial LGR factors, not a promise for any job. For the drying steps on a wet floor, see how to dry wet carpet after a leak or flood.

Converting liters per day to pints

Dehumidifiers sold in the UK and Europe are often rated in liters per day. One liter is 2.113 US pints, so a 12 L unit is about 25 pints (12 x 2.113 = 25.4) and a 20 L unit is about 42 pints (20 x 2.113 = 42.3). That is our calculation, and it carries no test condition, so use it only to get a rough match against the pint ranges in the chart above.

Frequently asked questions

What size dehumidifier do I need for a 1,000 sq ft basement?

Between 20 and 50 pints per day, depending on dampness, per the ENERGY STAR dehumidifier page: 20 to 30 if slightly to moderately damp, 25 to 40 if very damp and 30 to 50 if wet. For a very damp basement, we would look at the AlorAir Sentinel HD90 for its 90 pint AHAM rating. For a modest one, the Sentinel HS35 at 35 pints AHAM is the minimum.

Is a 20 L dehumidifier more powerful than a 12 L?

Yes, if both are rated in the same way. By our calculation, 20 L is about 42 US pints and 12 L about 25. Check the test condition on each label first, because liter ratings are often given at warmer, wetter conditions than the AHAM point.

Should I use a bigger dehumidifier than the chart says?

Often yes. ENERGY STAR's page says it is better to oversize than undersize. A larger unit reaches the humidity setpoint sooner and then cycles off. The tradeoffs are price, weight and power draw, so stay within one row of the chart.

How big a dehumidifier do I need for a bedroom or an apartment?

A single bedroom or apartment room is a small space, usually slightly to moderately damp, which the ENERGY STAR page puts at 20 to 30 pints per day. Our range is built for crawl spaces and commercial work, so even the HS35, the smallest machine in this guide at 35 pints per day at AHAM, is more than most bedrooms need.

Would a dehumidifier help with COPD?

We cannot give medical advice and we make no health claims for any machine. Ask your doctor about humidity targets for your home. This guide covers sizing a machine for a space, not treating a condition.

What is the difference between AHAM and saturation ratings?

AHAM rates removal at 80F and 60% relative humidity. Saturation rates it at 90F and 90% relative humidity, a much wetter test, so the number is larger. Size by the AHAM figure and never compare one maker's AHAM number with another's saturation number.

How often should I empty my dehumidifier?

The HS35, HD90, Storm Elite and XD-165L have no bucket to empty. The HS35 and HD90 drain by gravity through a hose to a floor drain, sump or outside. The Storm Elite and XD-165L pump the water out through a hose. A bucket unit needs emptying whenever it fills, and ENERGY STAR notes most shut off automatically when the bucket is full.

Related guides

• Best Basement Dehumidifiers: Commercial-Grade Picks for Big, Cold or Wet Basements
• Best Crawl Space Dehumidifiers: Picks by Size, Height and Drainage
• How Much Does It Cost to Run a Dehumidifier? Watts, Hours and Cost per Day
• How Does a Dehumidifier Work? Refrigerant, LGR and Desiccant Explained