Dehumidifiers for Drying Clothes: Running Costs and Which Type to Buy

The short answer

Drying clothes indoors puts about two litres of water into your house per wash. A dehumidifier is the only method that collects that water rather than moving it somewhere else. A 20-litre-per-day compressor unit draws roughly 480W, so a five-hour laundry session uses 2.4kWh and costs about 63p at 26.11p per kWh.

That is more than a heated airer on its own. It is much less than any tumble dryer. And in a house that already has condensation on the windows every morning, it is doing a second job you would otherwise be paying for separately.

Running costs by type and size

Wattages are typical rated draw in continuous laundry mode, where the unit does not cycle. Cost is at 26.11p per kWh.

Worked example: 480W is 0.48kW, five hours gives 2.4kWh, and 2.4 × 26.11p = 62.7p.

Used seasonally rather than per load, the numbers get larger. Five hours a day from October to March, 182 days, on the 20-litre compressor unit comes to 437kWh and £114. That is a real line on the bill, and it is worth knowing before you leave one running all winter out of habit.

The pairing that actually works

Put a heated airer and a dehumidifier in the same small room, shut the door, and both jobs get easier. The airer warms the air so it can hold more moisture; the dehumidifier strips that moisture back out and returns drier, slightly warmer air to the room. Drying time roughly halves.

The combination costs about 14p more than the airer on its own and finishes in half the time with the water in a container rather than on your plaster. Against the tumble dryer it saves 30p a load and takes an hour longer.

Compressor or desiccant

Compressor units chill a coil until water condenses on it, the same physics as a fridge. That works well in a warm room and badly in a cold one, because there is less moisture in cold air to start with and the coil ices up. Below about 15C the extraction rate drops away, and most compressor units have a defrost cycle that eats into their running time.

Desiccant units pass air over a rotating wheel of moisture-absorbing material and then drive the water off with a small heater. Cold does not bother them. They also put out air a few degrees warmer than they took in, which is welcome in a garage and irritating in a bedroom in June. The bill is the price: roughly double the electricity per litre extracted.

Sizing, and why the litres figure lies

Extraction rates are measured at 30C and 80% relative humidity. No British house sits there. In a 18C room at 60% humidity you should expect somewhere between a third and a half of the rated litres. A unit sold as 20 litres a day will realistically pull 7 to 10 litres in normal use, which is still far more than a laundry load contains.

For a three-bedroom house with occasional condensation, 10 to 12 litres a day is enough. For regular indoor drying, or a house that steams up every morning, go to 20. Buying bigger than you need costs more to buy but not much more to run, because a well-sized unit spends more time cycled off.

Practical things that save money

• Fit the drain hose. Most units have a continuous drain outlet. Run it to a sink or a floor drain and the unit stops shutting off with a full tank halfway through the night.
• Use the humidistat, not the timer. Set a target of 50 to 55% relative humidity and let it cycle. Running flat out at a fixed setting wastes power once the room is dry.
• Spin faster. A 1600rpm spin leaves noticeably less water in the load than 1200rpm, and every litre you leave behind is time and electricity on the dehumidifier.
• Clean the filter. A clogged intake filter costs airflow, which costs extraction rate, which costs running hours.

Common questions

How much does a dehumidifier cost to run for drying clothes?

A 20-litre compressor dehumidifier draws around 480W, so five hours in laundry mode uses 2.4kWh and costs about 63p at the 26.11p per kWh cap rate. A smaller 12-litre unit at 300W costs about 39p for the same session. Desiccant models draw more, typically 600 to 650W, so the same five hours costs 78p to 85p.

Is a dehumidifier cheaper than a tumble dryer for drying clothes?

Yes, comfortably. A condenser tumble dryer costs about 91p a load and a vented one £1.18. A dehumidifier and a heated airer running together in a closed room dry a load in around three hours for roughly 61p, and a dehumidifier alone with a clothes horse costs about 63p over five hours. The dryer still wins on speed by a wide margin.

Compressor or desiccant: which should I buy?

Compressor if the room is heated, desiccant if it is not. Compressor dehumidifiers condense moisture on a cold coil, and that process loses efficiency as the room gets colder, falling off noticeably below about 15C. Desiccant models pull moisture onto a rotating absorbent wheel and work down to near freezing, but use roughly twice the electricity per litre extracted. Heated house, buy compressor. Garage, conservatory or unheated utility, buy desiccant.

What size dehumidifier do I need?

For a normal three-bedroom house with an occasional damp problem, a 10 to 12 litre per day compressor unit is enough. For drying laundry regularly, or for a house with persistent condensation, 20 litres per day gives you headroom. Ignore the litres figure as a promise: it is measured at 30C and 80% relative humidity, conditions a British home basically never reaches. In a 18C room at 60% humidity, expect roughly a third to a half of the rated extraction.

Should I run a dehumidifier with the window open?

No. A dehumidifier is trying to dry a fixed volume of air, and an open window gives it the whole outdoors to work on. Close the door and the window in the room you are drying in, run the dehumidifier, and ventilate the rest of the house normally. This is the opposite of the advice for drying with an airer alone, where you want ventilation because the water has nowhere else to go.

Does a dehumidifier heat the room?

A little, and it is not wasted. Almost all the electricity a dehumidifier uses ends up as heat in the room, plus the latent heat released as water vapour condenses. A 480W unit running for five hours puts roughly 2.4kWh of heat into the space, which in a small closed room is noticeable. That is one reason the airer and dehumidifier pairing dries faster than the sum of its parts.