Size calculator
Basement Dehumidifier Size Calculator
Find the dehumidifier size you need in pints per day from the floor area and how damp the space is, on the 2019 rating new units carry and on the old label, with drain options and what it will cost to run.
Use the result wisely
What this sizes
- Pints per day from ENERGY STAR’s current sizing chart.
- The old-label equivalent, from ENERGY STAR’s conversion table.
- The classic AHAM chart number as a cross-check.
- Drain or pump, running cost and the humidistat setting.
Sizing for humid air. Water coming through the walls or floor needs a drainage fix, not a bigger dehumidifier.
The short answer
For a damp basement under 2,000 sq ft, ENERGY STAR recommends 20–30 pints per day if it is moderately damp, 25–40 if very damp and 30–50 if wet; over 2,000 sq ft, at least 30, 40 or 50. Those are pints on the 2019 rating that every new dehumidifier now carries. A typical 1,000 sq ft very damp basement needs about 35 pints, which is a "60-pint" unit on the old label. When in doubt, go bigger: a larger unit reaches its setpoint and cycles off, while an undersized one runs nonstop.
Sources: ENERGY STAR dehumidifier buying guidance and capacity conversion table; DOE test procedure, 10 CFR 430 Appendix X1. Read 2026-09-30.
Size calculator
How damp is it, and how big is the space?
Results are in pints per day on the current (2019) rating that new dehumidifiers carry, with the old-label equivalent for comparing older units and listings.
The floor area the unit has to dry. For an open basement, the whole footprint; close doors to rooms you leave out.
Always feels and smells damp. Damp spots on walls or floor. About 75–90% RH.
Most portable units have a hose fitting. The drain or sump pit must sit lower than the unit's hose outlet and close enough to avoid a long hose across the floor (ENERGY STAR).
Optional. On a muggy week, how many pints does your current unit collect a day? Measured water beats any chart.
Running cost depends far more on hours than on the unit.
Default: 18.31¢/kWh, the US residential average for July 2026 (EIA).
Dehumidifier sizing charts
The current chart, and the old one everyone still copies
Two charts are in circulation and they are on different rating standards. Most websites copy the second one without saying so.
1. ENERGY STAR’s current chart (2019 rating)
| Condition without a dehumidifier | Under 2,000 sq ft | Over 2,000 sq ft |
|---|---|---|
| Slightly to moderately damp (50–75% RH) | 20–30 | 30+ |
| Very damp (75–90% RH) | 25–40 | 40+ |
| Wet (90–100% RH; seepage, sweating, laundry drying) | 30–50 | 50+ |
ENERGY STAR buying guidance, read 2026-09-30. Pints per day, minimum capacity for a portable dehumidifier on the 2019 DOE rating. ENERGY STAR adds: it’s better to oversize than undersize.
2. The classic AHAM chart (old 80°F rating)
| Condition | 500 sq ft | 1,000 sq ft | 1,500 sq ft | 2,000 sq ft | 2,500 sq ft |
|---|---|---|---|---|---|
| Moderately damp | 10 | 14 | 18 | 22 | 26 |
| Very damp | 12 | 17 | 22 | 27 | 32 |
| Wet | 14 | 20 | 26 | 32 | 38 |
| Extremely wet | 16 | 23 | 30 | 37 | 44 |
Association of Home Appliance Manufacturers chart as ENERGY STAR published it until about 2019 (archived December 2012). Pints per day on the old rating.
Old label vs new label
Why a 70-pint dehumidifier became a 40-pint one
Capacity is the water a unit removes in 24 hours at fixed test conditions. Until 2019 portable units were tested in 80°F air at 60% relative humidity. Since June 13, 2019, the federal test (10 CFR 430, Appendix X1) uses 65°F at 60% for portable units and 73°F at 60% for whole-home units. Cooler air holds less water, so the same machine earns a smaller number. Nothing about the hardware changed.
That is why older articles and some listings still talk about “70-pint” basement units: on today’s rating that class of machine is 40–45 pints. The largest portable on ENERGY STAR’s table is a 90-pint old label, 55 pints new. When a listing doesn’t say which rating it uses, compare it against the conversion table.
The 65°F test is closer to a real basement, so the new number is the better guide to what the unit will do down there.
| Portable, old label | New (2019) rating | Whole-home, old | New |
|---|---|---|---|
| 30 | 20 | 80 | 70 |
| 40 | 25 | 100 | 85 |
| 50 | 30 | 120 | 100 |
| 55 | 30–35 | 140 | 115 |
| 60 | 35 | 160 | 135 |
| 70 | 40–45 | 200 | 170 |
| 90 | 55 | — | — |
ENERGY STAR “Dehumidifier Testing and Capacity” — its “rough correlation”; individual models vary. The calculator interpolates between rows.
Drain, pump or whole-house
Getting the water out, and when a portable isn’t enough
Drain and pump options
- Bucket. Every portable has one, and shuts off when it’s full. In a basement that needs drying all season, the bucket is the reason the unit stops working.
- Gravity hose. Most portables take a garden-hose fitting. Run it to a floor drain or the sump pit, which must sit lower than the hose outlet. ENERGY STAR advises placing the unit close enough to avoid a long hose across the floor.
- Built-in pump. Pump models push water up and out to a laundry sink, a window or across the room. Basement dehumidifiers with a pump are worth the extra cost when there is no drain below the unit.
- Safety. Plug into a grounded outlet, keep hoses away from cords and outlets, and don’t route water near electrical equipment.
Portable or whole-house?
ENERGY STAR suggests a whole-home unit if you live in a humid climate, have central air and see humidity above 55% throughout the house, not just downstairs. Whole-home units connect to the ductwork, drain to a floor drain or condensate pump, and should be sized and installed by an HVAC contractor. They also have their own federal efficiency minimums, set by case volume: 1.77 L/kWh up to 8 cu ft and 2.41 above it.
For a large basement alone, two portables in separate areas can dry it more evenly than one big unit in a corner. Basements where air doesn’t move need circulation as much as capacity: see basement ventilation.
Running cost
What a dehumidifier costs to run
Efficiency is the integrated energy factor (IEF): liters of water removed per kWh, including the power the unit draws while it idles. Higher is better. ENERGY STAR units, under the Version 6.0 criteria in effect since October 1, 2025, must beat the federal minimum in every size class.
The calculator uses DOE’s own arithmetic: rated pints × 1.04 lb per pint × 0.454 kg per lb, over the hours it runs, divided by the IEF. DOE’s test assumes 1,095 hours of dehumidifying a year. A 35-pint ENERGY STAR unit run that long uses about 375 kWh, about $69 at 18.31¢ per kWh. A wet basement that keeps the unit running half of every day for six months doubles that.
| Capacity (2019 rating) | Federal minimum IEF | ENERGY STAR minimum IEF |
|---|---|---|
| 25 pints/day or less | 1.3 | 1.7 |
| 25.01–50 pints/day | 1.6 | 2.01 |
| Over 50 pints/day | 2.8 | 3.3 |
Portable dehumidifiers. DOE minimums: 10 CFR 430.32(v)(2). ENERGY STAR: Version 6.0, effective October 1, 2025.
Setpoint
What to set it to, and when it isn’t a humidity problem
EPA advises keeping indoor humidity below 60%, ideally 30–50%; ENERGY STAR gives the same 30–50%. In a basement, set the humidistat around 45% to hold about 50% in summer and confirm with a separate hygrometer, since built-in sensors read the air the unit just dried. Seasonal targets and the dew-point math are in what humidity a basement should be.
Below 65°F, frost can form on the coils, and the compressor cycles without removing water. In a cool basement, look for a unit rated for low temperatures with automatic defrost.
FAQs
Dehumidifier size: common questions
What size dehumidifier do I need for a basement?
On today's 2019 rating, ENERGY STAR recommends 20–30 pints per day for a moderately damp space under 2,000 sq ft, 25–40 for very damp and 30–50 for wet. Over 2,000 sq ft, at least 30, 40 or 50. A 1,000 sq ft basement that always smells damp lands around 35 pints.
What size dehumidifier do I need for 1,000 sq ft?
About 25 pints per day if it is only damp in humid weather, 35 if it is always damp, and 40 if walls sweat or there is seepage, on the 2019 rating. On old labels those are roughly 40, 60 and 65 pints.
What size dehumidifier for a 2,000 sq ft basement?
At the top of ENERGY STAR's small-medium range: about 30 pints for moderately damp, 40 for very damp and 50 for wet (2019 rating). For a wet 2,000 sq ft basement, two units in separate areas or a ducted whole-home unit may dry it more evenly.
Is it bad to oversize a dehumidifier?
Not for a basement. ENERGY STAR says it is better to oversize than undersize. A larger unit reaches the humidistat setting and cycles off; an undersized one runs nonstop and never gets the space dry. The main cost of oversizing is the purchase price.
How many square feet does a 50-pint dehumidifier cover?
On the 2019 rating, 50 pints is the top of ENERGY STAR's range for a wet space under 2,000 sq ft and its minimum for a wet space over 2,000 sq ft. A 50-pint unit on the old label is only about 30 pints on the new rating, which suits a moderately damp space.
Is a 70-pint dehumidifier the same as a 50-pint?
No. ENERGY STAR's conversion table puts a 70-pint unit on the old 80°F test at 40–45 pints on the 2019 65°F test. A 50-pint unit on the new rating is a bigger machine, about 80 pints on the old label. Compare listings on the same rating.
Do I need a dehumidifier with a pump?
Only if there is no floor drain or sump pit lower than the unit. A gravity hose to a drain is simpler and has nothing to fail. If the water has to go up to a sink or out a window, buy a pump model or add a condensate pump.
How much does it cost to run a basement dehumidifier?
It depends mostly on hours. Using DOE's 1,095-hour test assumption, a 35-pint ENERGY STAR unit uses about 375 kWh a year, about $69 at the July 2026 US average of 18.31¢ per kWh. Running half of every day for six months roughly doubles that.
Related pages
Where to go next
What humidity should a basement be?
Seasonal targets, dew point and the plastic-sheet test.
Read nextBasement ventilation
When fresh air dries a basement and when it adds moisture.
Read nextMusty basement smell
Mold and mildew odor: humidity, hidden water or both.
Read nextBasement vapor barriers
Where a barrier helps a damp basement and where it traps water.
Read nextCrawl space dehumidifier calculator
Our sister site’s calculator for crawl spaces, which run colder and wetter.
Read nextBasement water source diagnostic
If it’s water coming in, find out from where.
Read nextMethodology
How this calculator works
Size. ENERGY STAR gives a pints-per-day range for three conditions under 2,000 sq ft and a minimum above it. Under 2,000 sq ft the calculator places you in the range by floor area (the low end near 0 sq ft, the high end at 2,000). “Extremely wet”, which ENERGY STAR folds into “wet”, starts halfway up the wet range. Above 2,000 sq ft it starts at ENERGY STAR’s minimum and grows it in step with the AHAM chart’s own increase with area. A measured daily collection from your current unit can raise the answer, never lower it. Results round up to the next 5 pints.
Ratings. Old-label equivalents and the AHAM conversion use ENERGY STAR’s capacity table, interpolated between rows (the 30–35 and 40–45 rows use their midpoints) and scaled proportionally outside it, which we flag.
Running cost. Rated capacity converted to liters with DOE’s constants (1.04 lb per pint, 0.454 kg per lb), spread over your run hours, divided by the minimum IEF for that size class (DOE or ENERGY STAR), times your electricity price. It assumes full rated output; real basements below 65°F or drier than the test remove less water per hour.
A sizing guide, not a moisture assessment. Charts can’t see air leaks, laundry, a sump pit without a lid or water coming through the walls. If a correctly sized unit can’t hold 50%, look for the source.
Sources checked: 2026-09-30. Crawl spaces have their own calculator on our sister site, crawlspacefixes.com.
Sources
Sources
- ENERGY STAR — Dehumidifiers: buying guidance (capacity chart, whole-home guidance, 30–50% RH, operating temperature)
- ENERGY STAR — Dehumidifier Testing and Capacity (old vs new capacity table)
- ENERGY STAR (archived Dec 2012) — dehumidifier capacity chart, source: Association of Home Appliance Manufacturers (AHAM)
- ENERGY STAR — Dehumidifiers key product criteria, Version 6.0 (effective Oct 1, 2025)
- 10 CFR 430 Subpart B, Appendix X1 — DOE dehumidifier test procedure (65°F/73°F at 60% RH; 1,095 hours)
- 10 CFR 430.32(v) — federal dehumidifier efficiency standards
- EPA — A Brief Guide to Mold, Moisture, and Your Home (below 60%, ideally 30–50%)
- U.S. Energy Information Administration — Electric Power Monthly, Table 5.6.A (residential average price, July 2026)