On this page
Homeowners choose between a portable unit that sits in one room and a whole-home dehumidifier connected to the ductwork, which an HVAC technician installs. Either way the target is the one Health Canada sets out: indoor relative humidity between 30% and 50%.
This page compares the two types, explains sizing and drainage, what ENERGY STAR certification tells you and how to maintain the machine, and why no dehumidifier can make up for water coming through the foundation.
Portable vs whole-home dehumidifiers: drying one room or the whole house
Natural Resources Canada describes portable dehumidifiers as units that treat a single room and can be moved easily, and whole-home dehumidifiers as systems that use the home's air ducts to dry one or more rooms and are often permanent. ENERGY STAR certifies both kinds.
A portable unit suits a basement, a laundry room or a cottage that turns clammy every summer. A whole-home unit makes more sense when several levels feel damp, when a finished basement is part of the living space, or when emptying buckets and moving machines around has worn thin. It usually sits near the furnace or air handler and ties into the duct system, so it needs a technician to plan the connection, a permanent drain and a proper electrical supply.
- Portable: plugs into an ordinary outlet, drains into a bucket or through a hose, and can follow the problem from room to room.
- Portable: you hear it in the room where it runs, and it mainly dries the space it sits in, especially with the doors closed.
- Whole-home: quieter in living areas because the machine is in a mechanical room, and it treats the air the ductwork reaches.
- Whole-home: calls for an assessment of the ducts, the drain route and the wiring, and any new circuit is a job for a licensed electrician.
Signs your basement or home needs a dehumidifier
Excess humidity below grade rarely shows up as water on the floor. It shows up as smells, condensation and slow damage to whatever is stored down there. A hygrometer, a small gauge that reads relative humidity, turns a hunch into a number you can act on.
- A musty, earthy smell that comes back every summer.
- Beads of water on cold-water pipes, the toilet tank or the concrete walls on humid days.
- Mildew on stored cardboard, fabric, leather or wooden furniture.
- Hygrometer readings that stay above 50% for days, the point at which Health Canada suggests running a dehumidifier.
- Condensation forming on windows or other cold surfaces, another trigger Health Canada names.
Summer basement humidity: keeping indoor air between 30% and 50%
Health Canada recommends keeping indoor relative humidity between 30% and 50%, and its mould guide advises running a dehumidifier in damp areas such as basements, and whenever moisture condenses on cold surfaces or humidity rises above 50%. Summer is when basements struggle: warm outdoor air carries a lot of moisture, and when it meets cool foundation walls and floors its relative humidity climbs and water can condense.
In winter the picture usually reverses, since cold outdoor air holds little moisture and heated indoor air tends to run dry. Many homes only need a dehumidifier from late spring to early fall, but a basement drying out after a flood, new concrete or a lot of indoor laundry can need one longer. Let the humidistat and a hygrometer guide you rather than a fixed schedule.
- Keep basement windows closed on hot, muggy days while the dehumidifier runs, so it isn't fighting fresh humid air.
- Vent the clothes dryer outdoors and avoid hanging laundry to dry in the basement.
- Remember that air conditioning also removes moisture, as Health Canada notes; a dehumidifier covers the cool basement that the cooling system barely reaches.
Sizing a dehumidifier and planning drainage: hoses, floor drains and condensate pumps
Natural Resources Canada explains that a dehumidifier's capacity is usually given in litres per day and depends on two factors: the size of the space and its current conditions. A large, very wet basement needs more capacity than a small room that is only slightly clammy, and a unit that is too small runs all day without reaching its setting. For a whole-home model, the technician also looks at the volume of the house, the ductwork and how humidity differs from one level to the next.
Drainage deserves as much thought as capacity. A full bucket shuts the unit off until someone empties it, so most basement installations drain continuously instead.
- Gravity drain: a hose runs from the unit's drain fitting downhill to a floor drain, laundry tub or sump pit.
- Condensate pump: lifts the water to a drain when none sits lower than the unit, which is common with whole-home models and finished basements.
- Whole-home units are normally connected to a permanent drain line, often near the furnace and air-conditioner condensate drains.
- Placement: Natural Resources Canada says units with top-mounted air discharge can stand against a wall, while others need space away from walls and furniture.
Energy use and ENERGY STAR certified dehumidifiers
A dehumidifier in a damp basement can run for long stretches all summer, so efficiency matters. Natural Resources Canada says an ENERGY STAR certified dehumidifier uses nearly 15% less energy on average than a standard model. Every certified model has a built-in humidistat: you set the relative humidity you want, and once the room reaches it, the unit cycles on and off to hold that level.
Setting the humidistat lower than you need burns electricity without making the space any healthier. Choose a setting within the 30% to 50% range, then adjust it based on what the hygrometer shows and whether condensation or mustiness returns. Natural Resources Canada's list of certified dehumidifiers is a good place to compare models.
Why a dehumidifier won't fix water leaking into the basement
A dehumidifier deals with moisture that is already in the air. It can't stop liquid water from coming through a cracked foundation, seeping in where the floor meets the wall, or rising through a slab where drainage has failed. Running one against an active leak mostly hides the problem: the room feels drier while the wall behind the finished drywall stays wet.
Puddles after heavy rain or snowmelt, damp patches low on the walls, white chalky deposits on the concrete or wet floor edges all point to water entry. Deal with that first by checking gutters, downspouts and grading, then have the foundation assessed; our basement waterproofing page covers the options, from crack repair to interior and exterior drainage. Once the water is stopped, a dehumidifier is the right tool for keeping the space dry.
Dehumidifier maintenance: filters, coils, buckets and drain lines
Natural Resources Canada advises keeping dehumidifier filters clean and checking them regularly so air can flow freely. The rest of the routine is short and set out in the owner's manual. Unplug a portable unit before cleaning it.
- Filter: vacuum or rinse a washable filter, or replace a disposable one, as often as the manual says, and more often in a dusty basement.
- Bucket: empty it and wipe it out so standing water doesn't turn slimy or smelly.
- Hose and pump: flush the drain line and check the pump's reservoir each season so sludge doesn't block them.
- Coil: frost on the coil in a cool basement points to a clogged filter or a room colder than the unit is designed for, so check the manual's operating limits.
- Whole-home units: include the dehumidifier in the furnace or air-conditioner service visit so the technician checks its filter, coil, drain and controls.
Dehumidifiers: frequently asked questions
What humidity should I set my basement dehumidifier to?
Health Canada recommends indoor relative humidity between 30% and 50%. Set the humidistat within that range, check a hygrometer after a few days, and lower the setting if condensation or a musty smell persists.
Should I buy a portable or a whole-home dehumidifier?
A portable unit is usually enough for one damp basement or room. A whole-home model, installed in the ductwork by an HVAC technician, suits houses where several levels stay humid or where a finished basement is lived in every day.
Can a dehumidifier drain on its own without emptying the bucket?
Yes. Most models can drain continuously through a hose to a floor drain, laundry tub or sump pit. When the drain is higher than the unit, a condensate pump lifts the water to it.
Will a dehumidifier get rid of mould?
No. Drier air helps keep mould from coming back, but existing growth has to be cleaned or removed and its moisture source fixed. Our mould remediation page explains when to call a professional.
Why does my basement still smell damp with the dehumidifier running?
The unit may be too small for the space, its filter or coil may be clogged, or humid air may be coming in through open windows or doors. Water entering through the foundation is another common cause, and no dehumidifier can fix that.
Sources
Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides