Dehumidifiers in Thailand 2026: what size, and the real running cost

Dehumidifiers are something people buy at the start of the rainy season and are often disappointed by, for two reasons: they buy the wrong size, and they do not realise what it costs to run.

This article fixes both — how to size one to the actual room, and the electricity arithmetic laid out plainly, which almost no review provides even though it is large enough to change the decision.

Aim at a number, not at a feeling

Before buying anything, know what you are aiming for. The US EPA recommends keeping indoor relative humidity below 60%, and within 30–50% where possible.

• Above 60%, condensation starts forming inside the building, which is the condition mould needs.
• 30–50% is the band that avoids mould and dust mites without being uncomfortably dry.
• Below 30% is too dry — dry throat and skin — and unnecessary in Thailand.

⚠️ Thai rainy-season humidity often sits at 75–90%, well above the threshold. That does not mean buying the biggest machine: the goal is to get below 60%, not as low as possible. Every extra percentage point you pull out is more electricity paid for.

Spending 200–500 baht on a hygrometer before buying a dehumidifier is the best-value advice in this article. Some rooms that feel "stuffy" actually have a ventilation problem rather than a humidity problem, and a dehumidifier will not fix that.

Photo: Asurnipal — CC BY-SA 4.0 (Wikimedia Commons)

Running cost: the number nobody quotes

This is the part that most changes the decision. A dehumidifier is not something you switch on briefly — it has to run for hours to do anything, and it draws 240–980 watts.

Costed at a 4.62 baht marginal rate (find your household's rate in our electricity saving article):

Photo: Unknown — CC CC0 (rawpixel)

The figure worth pausing on: a 12 L machine costs around 7,990 baht. Run 8 hours a day through a six-month rainy season, it uses roughly 1,800 baht of electricity a year — about 22% of its purchase price, every year. By year five the electricity has cost more than the machine did.

That is not an argument against buying one. It is an argument for buying the right size and running it only when needed, rather than leaving it on around the clock all season.

How to cut a dehumidifier's running cost

• Choose a model with an auto humidistat so it stops when it reaches the target, and set that target to 55–60% rather than the minimum.
• Close the room's doors and windows, or the machine is trying to dehumidify the whole neighbourhood.
• Run it only in the room that has the problem, not room by room around the house.
• Connect the drain hose. A full tank stops the machine, so you end up running it longer for the same result.

Choosing the capacity

"Litres per day" is how much water the unit can pull from the air in a day under test conditions. It is useful for comparing sizes, but you will always get less than the box says in real life, because test conditions are hotter and more humid than your room.

⚠️ Do not oversize. A bigger machine always uses more electricity and does not dry the room proportionally faster. If a room is genuinely very damp, the cheaper route is fixing the cause — a leak, or adding an extractor fan — before moving up a size. See our article on damp and mould.

Compressor or desiccant

For a typical Thai home, compressor is the answer, because our air is warm nearly all year, which is exactly where compressors work best — and a desiccant unit's waste heat is a clear disadvantage in a room that is already hot.

Desiccant and mini units suit small enclosed spaces like a wardrobe or camera cabinet, where quietness and light weight matter more than efficiency.

Already running air conditioning? You probably do not need one

Worth asking before buying, and the answer is usually no.

Photo: Daniel Ramirez from Honolulu, USA — CC BY (wikimedia)

Air conditioning cools by chilling air until moisture condenses out of it — exactly the same principle as a compressor dehumidifier. The water running from the AC's drain pipe is humidity removed from the room. A room that is air conditioned regularly usually does not have a humidity problem to begin with.

A dehumidifier earns its keep in these situations instead:

• Rooms that are not air conditioned — storage rooms, shrine rooms, under stairs, the garage.
• Rainy-season weather that is humid but not hot enough to want the AC on, which describes much of July to October in Thailand.
• Rooms needing tight humidity control — camera gear, musical instruments, books, leather.
• Where laundry dries indoors, which adds moisture directly. Pair it with a clothes dryer, or pick one or the other on budget.

⚠️ The AC's "dry" mode is not a dehumidifier. Dry mode runs the compressor with a low fan speed to pull moisture without over-cooling. It does work, but it still draws air-conditioner power (1,200 W and up), several times a 270 W dehumidifier. If the only goal is lowering humidity, the dehumidifier is far cheaper.

Cheaper alternatives to try first

Before spending thousands, three things cost far less and genuinely solve the problem in many cases:

Note the gap: a 1,500 baht extractor fan costs 28 baht a month to run; an 8,000 baht dehumidifier costs 300. That is roughly ten times more on both counts. If the room's problem is "air does not move", an extractor fan addresses it more directly and far more cheaply.

⚠️ But there is a case where ventilation does not help: when the outside air is more humid than the room, which happens on any rainy Thai day. Opening the windows then brings humidity in. That is where a dehumidifier clearly wins — and it is why the hygrometer earns its keep, because it tells you which kind of day it is.

The dampest spots in a Thai house

If you are buying one machine, it helps to know where to put it. In rough order of how often they cause trouble:

1. Bathrooms and the areas next to them — shower steam is the biggest single moisture source in a house. An extractor fan works better here.
2. Storage rooms, under stairs, rooms with no window — no airflow, so moisture sits.
3. Ground floors in contact with the earth — moisture wicks up, common in older houses without a damp course.
4. Wardrobes and built-in cabinets — sealed spaces nobody opens for days; better suited to sachets than a machine.
5. Rooms where laundry dries indoors — one load of wet washing releases several litres into the room.

⚠️ Point 5 matters more than people think. Drying laundry in the bedroom during the rainy season adds moisture directly, and then running a dehumidifier to take it out means paying twice. If that is your routine, a clothes dryer may work out better.

Maintenance and lifespan

A dehumidifier has a compressor like an air conditioner or a fridge, so it is looked after similarly:

• Rinse the filter every 2–4 weeks. A clogged filter cuts airflow across the coil, so it removes less moisture for the same electricity.
• Empty and wash the tank regularly. Water standing for days breeds smells and growth.
• Leave clearance around it, usually at least 20–30 cm on the vented sides.
• Never tip it on its side. If you have to move it, stand it upright for several hours before plugging it in, exactly as with a fridge, so the compressor oil settles back.
• Typical life is about 5–10 years, depending on hours and care — another reason to count the electricity across that life as part of what you are really paying.

What to check before buying

• Auto humidistat — set a target and it stops itself. The single biggest factor in running cost.
• Continuous drain connection — transformative if you plan to run it all day.
• Tank size — a small tank means frequent emptying, and the machine stops while you are out.
• Noise in dB — for a bedroom, look for under 45 dB.
• Wheels and a handle — anything 20 L and up is heavy to move without them.
• Filter — some have an air filter that needs regular rinsing, like an AC.

Common mistakes

Expecting the number on the box. "20 L/day" is measured in conditions more humid and warmer than your room. Getting less is normal, not a fault.

Running it with the windows open. You are trying to dehumidify the province. The electricity goes and the room barely changes.

Buying a machine instead of fixing the cause. If the room is damp because of a leak, a seeping wall or no ventilation, a dehumidifier is paying electricity forever to mask a symptom.

Forgetting it gives off heat. Both types do, desiccant more. A small sealed room can become noticeably warmer.

Putting it against a wall or in a corner. It needs air in and out; leave the clearance the manual specifies.

Summary

1. Buy a hygrometer first and check whether the room really is above 60%. Sometimes the problem is ventilation, not humidity.
2. Size it to the actual room — 12–16 L/day covers an ordinary bedroom. Do not buy bigger "just in case".
3. Count the electricity — around 300–450 baht a month for a small unit, and more than the purchase price across five years.
4. If that room already runs air conditioning, you probably do not need one.
5. Choose compressor, with an auto humidistat and a drain port. Those three cover almost every Thai household need.

Sources

• US EPA — Mold Course Chapter 2: humidity and mould growth
• US EPA — Brief Guide to Mold, Moisture and Your Home
• Thairath — dehumidifier round-up (reference prices and specifications)
• LG Thailand — do you need a dehumidifier in the bedroom?
• MEA — current Ft announcement

Prices and specifications are reference figures as of September 2026 and change. Electricity costs multiply rated power by assumed running hours at a 4.62 baht marginal rate, so they are estimates for comparison, not what your own machine will draw.