Dehumidifiers: How to Buy the Right One
A dehumidifier is bought to solve a problem — damp walls, condensation on windows, musty air, mould — and the mistake people make is buying on price rather than on whether it can actually extract enough moisture for the space. Get the capacity and the type right for your conditions and the rest is detail.
Key takeaways
- Capacity (pints/day) must match your room size and how damp it is.
- Refrigerant vs desiccant depends on the temperature where you'll use it.
- Continuous drainage turns a daily chore into a set-and-forget appliance.
- Fix the source of moisture too — a dehumidifier manages damp, it doesn't cure leaks.
Begin with capacity, rated in pints of water removed per day, because an undersized unit runs constantly and never wins. Capacity should reflect both the room's size and how damp it is: a slightly damp medium room needs far less than a wet basement of the same size. Manufacturers publish sizing charts that cross room area with dampness level — use them rather than guessing, and lean towards more capacity if the space is genuinely wet.
Then pick the right technology for your temperatures. Refrigerant (compressor) dehumidifiers are the efficient choice for warm and normal rooms but lose effectiveness as it gets cold. Desiccant models work well in cold spaces like garages and unheated rooms and run quieter, but use more electricity. Matching the type to where the unit will actually live is what stops a capable dehumidifier from underperforming.
What actually matters when buying a dehumidifier
Capacity, sized to room and dampness
The headline pint rating is removal per day under test conditions. To size correctly, combine your room area with how damp it feels — 'moderately damp' (musty smell), 'very damp' (visible moisture), 'wet' (standing water or seepage). A larger-capacity unit in a moderately damp room reaches the target humidity faster and then idles, which is more efficient than a small unit running flat out.
Refrigerant or desiccant?
Refrigerant dehumidifiers cool a coil to condense moisture and are the efficient default for living spaces and anywhere reliably above about 15 °C. Desiccant dehumidifiers absorb moisture with a drying wheel, keep working in cold rooms, weigh less and run quieter, but draw more power. For a heated home choose refrigerant; for a cold garage or conservatory, desiccant.
Drainage: tank or continuous
A tank fills and must be emptied — tolerable for occasional use, tedious for a damp basement. Continuous drainage lets the unit drain via a hose into a sink or drain so it runs unattended; some pump water upwards to a higher outlet. If you'll run it daily, continuous drainage is the feature that makes the appliance genuinely hands-off.
Humidistat and auto control
A built-in humidistat lets you set a target humidity (around 45–55% is comfortable and discourages mould); the unit then cycles to hold it rather than running forever. Without one, you either run it constantly or guess. Auto-restart after a power cut and a defrost mode for cooler rooms are worth having.
Noise and placement
If the dehumidifier sits in a bedroom or living area, noise matters — refrigerant models have a compressor hum, desiccant models are generally quieter. Air needs to circulate around it, so it can't be crammed into a cupboard. Check the decibel figure for living spaces.
The jargon, decoded
The key terms are few but easy to misread. Here's what they mean.
| Term | What it means |
|---|---|
| Pints/day | Water removed per day under test conditions. The headline capacity; real-world extraction is usually lower. |
| Refrigerant | Compressor type that condenses moisture on a cold coil. Efficient in warm and normal rooms, weaker in the cold. |
| Desiccant | Uses a drying wheel to absorb moisture. Works in cold rooms, quieter and lighter, but uses more electricity. |
| Humidistat | A sensor and control that holds a target humidity, cycling the unit instead of running it non-stop. |
| Continuous drainage | A hose outlet so the unit drains itself into a sink or drain and never needs emptying. |
| Built-in pump | Pushes collected water upward, letting you drain to a higher sink or window — useful in basements. |
How much should you spend? Budget tiers
Capacity and drainage features drive the price. Here's the lay of the land.
| Tier | Typical price | What you get |
|---|---|---|
| Budget | $80 – $150 | Small-capacity units or compact desiccant models for a single damp room, wardrobe or caravan. Tank-only, basic controls. Fine for light, localised damp. |
| Mid-range | $180 – $300 | Larger refrigerant units with a humidistat, continuous-drainage option, auto modes and laundry-drying settings. The right choice for a damp room, basement or whole-floor use. |
| Premium | $350 + | High-capacity units with a built-in pump, smart controls and strong cold-weather performance. Worth it for persistently wet basements or large, problem spaces. |
Browse current dehumidifier listings on Amazon →
Pick by your conditions, not the headline number
Two rooms of the same size can need very different dehumidifiers. A heated living room with seasonal condensation needs a modest refrigerant unit with a humidistat. A cold, wet basement needs more capacity, continuous drainage and possibly a pump — and if it's unheated, a desiccant model. Diagnose the temperature and the dampness level first, then size up rather than down. Crucially, a dehumidifier manages moisture; if damp comes from a leak, failed seal or rising damp, fix the source too or the unit will run forever.
Tip: set the humidistat to around 50%. Below about 45% you waste energy and dry the air uncomfortably; above 60% you invite mould. The 45–55% band is the comfortable, mould-resistant sweet spot.
Common mistakes (and how to avoid them)
1. Buying too little capacity
An undersized unit runs non-stop, costs more to run and never reaches target humidity. Size to the room and its dampness level using the maker's chart, and round up for genuinely wet spaces.
2. Using a refrigerant unit in the cold
Compressor dehumidifiers lose effectiveness below roughly 15 °C and can frost up. For garages, conservatories and unheated rooms, a desiccant model is the right tool.
3. Skipping continuous drainage for daily use
Emptying a tank twice a day gets old fast. If you'll run it continuously, buy a model with a drain hose outlet — or a pump if the only drain is higher up.
4. Treating the symptom, not the cause
A dehumidifier won't fix a leaking gutter, failed damp-proof course or unventilated bathroom. Address the moisture source as well, or you'll mask a problem that keeps getting worse.
When is the best time to buy?
Dehumidifiers are most in demand — and most expensive — in damp autumn and winter months. Prices ease in late spring and summer, and the usual Black Friday and Prime Day events bring the sharpest discounts. If you can foresee winter condensation, buying in the warmer months saves money and avoids the seasonal stock shortages.
Tip: our seasonal sale calendar maps the cheapest months for every major category, and the discount calculator tells you what a sale price really works out to.
Frequently asked questions
What size dehumidifier do I need?
Size it to both the room area and how damp the space is, using the manufacturer's sizing chart. A moderately damp medium room needs far less capacity than a wet basement of the same size. It's better to choose slightly more capacity than you think you need: a larger unit reaches the target humidity quickly and then idles, which is more efficient and quieter than a small unit running flat out all day.
Refrigerant or desiccant — which should I buy?
Choose by temperature. Refrigerant (compressor) models are the efficient choice for heated living spaces and anywhere reliably above about 15 degrees Celsius. Desiccant models keep working in cold rooms such as garages and conservatories, run quieter and weigh less, but use more electricity. For a normal heated home, refrigerant is usually best; for cold or unheated spaces, desiccant.
Will a dehumidifier stop damp and mould?
It will control the humidity that lets mould grow, and holding a room around 45 to 55 percent relative humidity discourages it. But a dehumidifier manages moisture in the air; it cannot fix the source. If damp comes from a leak, failed seal, poor ventilation or rising damp, you need to address that as well, or the unit will run endlessly while the underlying problem continues.
Is it expensive to run a dehumidifier all the time?
It can be, which is why a humidistat matters: it holds your target humidity and cycles the unit off instead of running constantly. Refrigerant models are generally more energy-efficient than desiccant ones in warm rooms. Sizing the unit correctly also helps, because a right-sized dehumidifier spends much of its time idling rather than working flat out.