Does a dehumidifier cool a room? (And when you need air con instead)

No, a dehumidifier doesn't cool a room. It actually makes it slightly warmer. A compressor dehumidifier blows out air about 2°C warmer than the air it takes in, and a desiccant model blows out air about 10 to 12°C warmer, according to Meaco, which makes both types. As Meaco's managing director put it to Homebuilding & Renovating: "The answer is definitely no."

Drier air can take the clammy edge off a sticky room, but at normal indoor temperatures that effect is small, and the dehumidifier's own heat cancels much or all of it in a closed room. If you want a room to actually get cooler, you need air conditioning, which removes heat and moisture and sends the heat outside.

The good news is they're not really rivals. A dehumidifier is the right tool for winter condensation, mould, and drying laundry; air con is the right tool for summer heat. Plenty of households sensibly own one of each.

Does a dehumidifier cool a room? Why it actually warms it

There are two kinds of dehumidifier, and both add heat.

A compressor (refrigerant) dehumidifier pulls air over a cold coil so the moisture condenses out, then passes that dried air back over the hot side of the same circuit before blowing it into the room. The air comes out about 2°C warmer than it went in.

A desiccant dehumidifier soaks up moisture with an absorbent wheel, then uses a heater to dry the wheel out again. The air comes out about 10 to 12°C warmer, and Meaco says these models "meaningfully" heat a room. Homebuilding & Renovating notes one can act as a gentle heater.

The physics is straightforward. Every watt of electricity a dehumidifier uses ends up as heat in your room. On top of that, when water vapour condenses back into liquid it gives off heat, about 0.68 kWh for every litre collected.

Here's a worked example. A MeacoDry Arete One 20L draws 216 W. Run it all day and it uses about 5.2 kWh of electricity (0.216 kW × 24 hours). If it collects 10 litres of water, condensing that releases roughly another 6.8 kWh (10 × 0.68). That's about 12 kWh of heat in total, about the same as leaving a 0.5 kW heater on for 24 hours. (Strictly speaking, that condensation heat was already in the room as humidity, so the room's total energy only rises by the electricity used. But the thermometer, and your skin, notice the full temperature rise.)

Compare a 2.5 kW split air conditioner taking 2.5 kW of heat out of a room with a dehumidifier putting about 0.2 to 0.6 kW in.

Does drier air make you feel cooler?

A little. Your body cools itself by sweating, and the Met Office explains that humid air slows down the evaporation of sweat, so the same temperature feels hotter when it's muggy. Expert Reviews makes the same point from the other side: a dehumidified room may feel cooler, but the temperature doesn't drop.

How much cooler does it feel? We ran the numbers through the standard thermal comfort model used in ISO 7730 and ASHRAE 55 (someone sitting down in light summer clothes, still air). At 26°C, dropping humidity from 70% to 40% makes the room feel slightly fresher, about 0.7°C cooler, or roughly a quarter of a degree for every 10 points of humidity. Both rooms sit inside the model's comfort band, so this is fine-tuning rather than the difference between sticky and comfortable.

That's a real but modest benefit, and in a closed room the heat the dehumidifier puts out will usually match or beat it. Humidity matters most at the hot, sweaty end of the scale, not at a typical 24 to 26°C.

Dehumidifier vs air conditioner: what each one does

Prices correct as of October 2026.

Does air conditioning dehumidify?

Yes, as a by-product of cooling. When room air passes over the cold indoor coil, any moisture in it condenses on the coil (the same way a cold can sweats on a summer's day) and drains away. A typical air conditioner puts roughly three quarters of its effort into lowering the temperature and a quarter into removing moisture. As a rough illustration, a 2.5 kW split running flat out would pull about 0.9 litres of water an hour out of the air.

One catch: an oversized unit that cools the room fast and then switches off doesn't run long enough to pull out much moisture. That's one reason sizing matters; our guide to what size air conditioning you need explains how to get it right.

What is dry mode?

Most splits and portables have a "dry" setting that runs the unit mainly to remove moisture. Daikin's manual for the Perfera puts it simply: "the system decreases the humidity in a room", and you can't adjust the temperature or fan speed while it's in that mode. Because the coil still runs cold, dry mode usually cools the room a bit too, which is great in a muggy summer and not much use in a chilly winter room. Exactly how it behaves varies by manufacturer, so check your manual.

Can you use a portable air conditioner as a dehumidifier?

Yes, and on paper they shift a lot of water. Rated maximums include about 22 litres a day for the Meaco MC9000 (0.9 litres an hour), up to 32 litres a day for the De'Longhi Pinguino EX100 in De'Longhi's 35°C, 80% humidity test (some retailers say 24), and up to 40 litres a day for the De'Longhi PAC EM77. That's more than most home dehumidifiers, which typically manage 12 to 20 litres a day.

There are two catches. Those figures are measured in hot, humid test conditions you'll rarely see indoors in Britain, and you're paying for 800 to 1,100 W of portable air conditioner to do a 150 to 260 W job. Whether the exhaust hose has to stay connected in dehumidify mode depends on the model. If the hot air isn't vented outside, the unit behaves like a dehumidifier and warms the room.

Running costs at the October 2026 price cap

All figures use the Ofgem price cap for 1 October to 31 December 2026: 26.32p per kWh (GB average, direct debit). There's no VAT on domestic electricity from 1 October 2026 to 31 March 2027, so don't compare this directly with the previous quarter's 26.11p, which included 5% VAT.

The sum: power in kW × hours × 26.32p.

So the Meaco 12L for eight hours is 0.157 kW × 8 × 26.32p, which comes to about 33p. Dehumidifiers with a humidistat switch off once they reach your target, so real costs are usually lower. Air conditioners rarely run flat out either: assuming 60% of full power for eight hours, a 1.0 kW portable costs about £1.26 a day and a 2.5 kW split averaging 0.47 kW costs about 99p.

Prices and rates correct as of October 2026. The energy price cap changes quarterly, so check current rates before budgeting.

The dehumidifier is cheaper to run, but it's doing a different job. For the full picture on air con bills, see are air conditioners expensive to run?

Which do you need?

It mostly comes down to the season and the problem you're trying to fix.

Summer heat: air conditioning

For a hot bedroom, a home office, or a top-floor flat in a heatwave, you want air conditioning. A dehumidifier will make things slightly worse. A portable unit is the no-installation option; a split system costs less to run per hour if you want a permanent fix. Our guides to the best portable air conditioners and bedroom air conditioning will help you choose.

If air con isn't on the cards this year, start with the free tricks in how to keep your house cool rather than switching on a dehumidifier.

Winter condensation, mould, and drying laundry: a dehumidifier

This is where a dehumidifier shines. Government guidance on damp and mould (from MHCLG with OHID and UKHSA) calls condensation from showering, cooking, and drying laundry "one of the most common causes" of damp, and says damp and mould can worsen asthma and other lung conditions. The same guidance is clear that the root problems are poor ventilation, heating, and energy efficiency, so use a dehumidifier alongside those fixes rather than instead of them. For the fixes themselves, from trickle vents to a little background heat, see our guide on how to stop condensation on windows.

Pick the type by the room's temperature:

• Compressor for heated rooms above about 15°C. They're cheaper to run but lose performance towards 10°C as the coil ices up; Meaco suggests a 20 or 25 litre model for rooms at 10 to 15°C.

• Desiccant for cold spaces such as garages, unheated conservatories, and rooms below 10°C. The Meaco DD8L, for example, works from 1°C, and the extra warmth it gives off is a bonus in winter.

For most homes, keeping indoor humidity around 40 to 60% is the usual target. Our guide to the ideal humidity in a house explains how to check yours with a cheap hygrometer. We cover what high humidity means for dust mites and allergies in our guide to whether air conditioning is bad for you.

Renting from a council or housing association in England? Under Awaab's Law, social landlords have had to investigate significant damp and mould within 10 working days since 27 October 2025. From 30 November 2026 a second phase adds more hazards, including excess cold and excess heat. It doesn't yet cover private renting.

Using both

Owning both is common and sensible: a dehumidifier for the winter months and air con (or its dry mode) for the summer. If you're thinking about a reverse-cycle split, it can heat in winter too. It doesn't dry the air while heating, but warmer rooms and surfaces mean less condensation, alongside good ventilation. Our guide to heating with air conditioning explains how that works, and the air-to-air heat pump grant may help with the cost.

Where should you not use a dehumidifier?

• In a hot, closed bedroom in summer as a way to cool down. It'll add heat.

• A desiccant model in a room that's already warm, since it blows out air 10 to 12°C warmer.

• A compressor model in a very cold space, such as an unheated garage in January, where it will struggle and keep defrosting.