Is a dehumidifier cheaper to run than an air conditioner?

Much cheaper. A domestic refrigerant dehumidifier draws roughly 150–500 W, versus 1,000–1,800 W for a portable air conditioner — so it costs about a third to a fifth as much per hour. A 300 W dehumidifier costs around 7p/hour in the UK; a 1,200 W portable AC costs about 29p/hour.

Does a dehumidifier cool a room?

No — it slightly warms it. A dehumidifier condenses moisture out of the air, but the latent heat released plus the compressor's own heat stay in the room, so the temperature creeps up by 1–3°C in a closed space. It makes humid air feel more comfortable, but it does not lower the temperature the way an air conditioner does.

Does an air conditioner remove humidity?

Yes. An air conditioner condenses moisture on its cold coil as a byproduct of cooling, and most units have a 'dry' or dehumidify mode that prioritises moisture removal at lower energy than full cooling. So an AC does both jobs; a dehumidifier does only one.

Should I buy a dehumidifier or an air conditioner?

If the air is genuinely hot, you need an air conditioner — a dehumidifier can't cool. If it's muggy or clammy but not very hot (common in UK summers), a dehumidifier is far cheaper to run, and removing the humidity may be all the comfort you need. If you have both problems, an AC handles them together.

Air Conditioner vs Dehumidifier: Which Do You Actually Need?

Published: May 25, 2026

They look similar and both have a compressor and a fan, but they solve different problems. The cheap mistake is buying the wrong one — so here’s the difference in watts, running cost, and physics.

What each one actually does

Air heat comes in two forms: sensible heat (temperature) and latent heat (the energy locked in water vapour, i.e. humidity).

An air conditioner removes both. It pumps heat out of the room (lowering the temperature) and condenses moisture on its cold coil as a side effect. The heat leaves through the exhaust hose or outdoor unit.
A dehumidifier removes only the moisture. It condenses water vapour, but the latent heat that releases — plus the compressor’s own heat — stays in the room. Net effect: it slightly warms the space (typically +1–3°C) while drying it.

So a dehumidifier can never cool. What it can do is make a given temperature feel more comfortable, because drier air lets sweat evaporate and raises the temperature you find tolerable.

The running-cost gap

This is where they really differ. A dehumidifier is a much smaller electrical load.

Appliance	Typical power	Cost/hour (UK 24.5p)	Cost/hour (US 16¢)
Refrigerant dehumidifier	150–500 W	~4–12p	~2–8¢
Portable air conditioner	1,000–1,800 W	~25–44p	~16–29¢

A dehumidifier typically runs at a third to a fifth of an air conditioner’s wattage, so if humidity (not heat) is your real problem, you’d be paying several times more to run an AC for a job a dehumidifier does for pennies.

When each one wins

It’s genuinely hot → air conditioner. Nothing else lowers the air temperature. Compare units by cost to run.
It’s muggy/clammy but not very hot → dehumidifier. Far cheaper, and removing humidity often restores comfort on its own. This is the common case in UK summers and in damp rooms.
Both → air conditioner. It cools and dehumidifies in one appliance; use the dry mode when you only need moisture removed.
Year-round damp, condensation, mould, drying laundry → dehumidifier. An AC doesn’t serve these at all.

The “dry mode” middle ground

Most air conditioners include a dry/dehumidify mode that runs the compressor with a low fan speed to wring out moisture using less energy than full cooling. It’s handy, but the unit is still an AC-sized appliance — a dedicated dehumidifier will remove moisture more cheaply if cooling isn’t needed.

Verdict: buy for the problem you actually have. Hot air needs an air conditioner; humid-but-mild air is a dehumidifier’s job at a fraction of the running cost.

Next: air conditioners ranked by running cost · air conditioner vs fan · how to reduce running costs