Dehumidifier Running Cost per Hour (kWh & Watts)

A dehumidifier helps your home feel better by cutting down on extra water in the air. This stops things like mould, too much damp, and excess moisture. A big benefit is you can use it to dry clothes indoors, and it often costs less than other ways.

You might ask, “How much does it cost to run one per hour, per day, or in a month?” This easy guide is here for you. The maths is broken down in plain English, so you know what you pay. You will read how things like wattage, humidity levels, and the duty cycle change what shows up on your bill. There’s also help for getting maximum efficiency when you set up a good drying area with your wet laundry on the rack.

If you still feel your rate is high–even after you make smart choices–remember to compare energy prices to find the best deal.

How do you calculate dehumidifier running cost?

The same simple formula works for any appliance:

• Power (kW) = watts divided by 1,000
• Energy used (kWh) = power (kW) times the number of hours
• Cost (£) = energy (kWh) times your unit rate, when pence per kWh is divided by 100

Example 1 (light room): A 200-watt light runs for 2 hours. This uses 0.2 times 2, which is 0.40 kWh. At 28 pence for each kWh, the total price is 0.40 × £0.28 = £0.11.

Example 2 (laundry mode): A 350-watt compressor is at work for 6 hours drying the wet clothes. In this time, it will use 0.35 × 6, which is 2.10 kWh. At 28 pence for each kWh, the cost will be £0.59.

Your result can change for a few reasons. Most dehumidifiers do not run at full power the whole time. The humidistat checks the humidity levels in the room. It then compares this to the level you set, like 50–55% RH. When the air is dry, the compressor will stop and sometimes only the fan runs. The machine may even turn off for a bit. The part of the time when the compressor is running is called your duty cycle. To find out the real cost, you need to use this formula: hourly cost × duty cycle × hours used.

Understanding “energy used” during the drying process

• When the room is very wet, or when you hang a load of laundry, the unit needs to work harder. The duty cycle goes close to 100%.
• When there is less excess moisture in the air, the machine runs in cycles. It uses less energy, even though it works for the same amount of time.
• Cold air can make the compressor coils freeze up. Defrosting takes more time and doesn’t get as much water out. Desiccant models don’t have icing problems but use more watts.

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Typical power ratings (watts) and where each type fits

Different kinds of technology work better in some rooms and at different times of the year. You need to look at the rating plate and read the instruction manual to see your real power rating and all the different modes.

“L/day” is a number that labs use for testing at a set temperature and humidity. In your home, the amount the machine takes out is less if your rooms are colder or already dry. You should use L/day to help compare sizes. It is not a guarantee.

Rule of thumb:

• A warm room or heated living space means a compressor will give you the best energy efficiency.
• A cold room (under about 10–15 °C) should use a desiccant. It will keep taking out water well and warms up the space a bit, too.

Dehumidifier cost per hour (plug-in tables)

Find your wattage in the column on the left. If your cost is different, put your amount in the formula.

At 18p / 28p / 38p per kWh

Duty cycle examples (what you actually pay):

• Maintenance drying in a heated lounge at 50–55% RH: A 250 W compressor will work about 30–40% of the time. This costs about 2–3p per hour if you pay 28p for each kWh.
• Laundry mode in a closed drying area with a fresh rack: The same compressor will work 70–100% of the time for the first few hours. It costs about 5–7p per hour.
• Cold utility room with a desiccant at 500 W: This costs 10–14p per hour at 28p/kWh. It takes moisture out of the air faster, which helps to balance out the higher power use.

How duty cycle shapes weekly and monthly costs

Let’s model two common scenarios at 28p/kWh.

Scenario A — Everyday moisture control

• Unit: 200 W compressor
• Schedule: 8 hours a day
• Average duty cycle: 35%
• Daily energy: 0.2 × 8 × 0.35 = 0.56 kWh
• Daily cost: £0.16 → ~£4.80/month (30 days)

Scenario B — Laundry support all winter

• Unit: This is a 350 W compressor used for laundry mode, running three evenings a week.
• Run: Each session lasts 6 hours and the compressor is on about 80% of that time.
• Weekly energy: 0.35 × 6 × 0.8 × 3 = 5.04 kWh
• Weekly cost: £1.41 which will be about £6.10/month

If those bills feel high, look at your tariff. A quick compare energy prices check can lower what you pay every hour. You do not have to change your daily habits.

Drying clothes indoors: the full workflow for faster drying time and less energy

A dehumidifier can cost less to use than traditional tumble dryers if you set it up right. Let’s look at how to lower energy use and make the drying process faster.

1. Prep the laundry (free wins)

• Run the highest safe spin cycle in the washing machine. Be sure to check the instruction manual for what’s safe for fabrics. Getting water out with the machine is the cheapest way.
• Give every item a good shake before you hang them up. This helps to open the fibres, so hot air from your heat pump dryer or the outlet of a dehumidifier can go through.

2. Build the drying area

• Put your clothes on a rack or a heated clothes airer. Make sure there are spaces between each item. Place thick clothes near the sides.
• Shut doors to keep the drying area small. You do not need to dry clothes across the whole house.
• For proper ventilation and to keep air quality good, open a window just a little. This will stop the place from feeling stuffy, but it will not let out much heat.

3. Place the dehumidifier

• Face the outlet so it points across the rack. This way, the air goes through the clothes, not just around them.
• Keep the intake area clear by leaving about 30–50 cm of space. If any grilles are blocked, the airflow will be less, and it takes longer to remove water from the clothes.

4. Choose settings

• Aim for 50–55% RH. Lower numbers do not often make things dry faster and will make household costs go up.
• Start with laundry mode or a stronger fan for the first hour. After that, switch to normal. This helps save kilowatt hours.
• Timer: Set it for 2–4 hours, check if things are done, and run it for longer only if you need to. Try not to leave it running all night unless you really have to.

5. Manage moisture

• Empty the water tank before you go to bed, or connect the continuous drain hose. A small tank can fill up fast and stop working. This will make it hard for the job to get done right.

Cost comparison for a load of laundry (28p/kWh)

Which is best?

• If you live in a small flat and do one load of laundry every day, you can use a heat pump dryer. You can also use a dehumidifier with a heated airer in a closed room.
• If you have a family with space and good weather, it is best to use an outdoor clothesline whenever you can. A dehumidifier can help if you cannot dry clothes outside.

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Compressor vs desiccant: deeper look at energy and performance

Compressor dehumidifiers

• How they work: A refrigeration loop pulls water out of the air by putting it onto a cold coil.
• Strengths: In warm rooms, these use low amounts of watts. They take out a lot of water for each kWh. On low fan, they are quiet.
• Limits: If the room is cold, the coil builds up ice. The unit then has to spend some drying time to melt the ice.

Desiccant dehumidifiers

• How they work: A rotor that likes water pulls in the moisture. A small heater heats up the water and sends it out to a drain.
• Strengths: They keep working even in the cold. The air that comes out feels a bit warm, so this can help a drying area.
• Limits: They use more power, so the cost per hour goes up. But they usually lower the total drying time in cold rooms.

Decision guide:

• Heated lounge/bedroom: A compressor (200–300 W) gives you the most efficiency.
• Shed/garage/spare room at 10 °C: A desiccant (400–600 W) works well, so you get reliable extraction.

Water tank, drainage and avoiding stoppages

A dehumidifier will stop working when the water tank is full. This wastes a lot of the good work it has done in the last hour. It also means it will take more time to reach the target RH level.

• Pick a tank size that works with your daily routine. A 2 to 4 litre tank is good for laundry at night.
• If you use your dehumidifier often, connect the drain hose to the sink or to a condensate pump. This way, you can forget about emptying the tank.
• If you see the tank is almost empty when your clothes feel damp, it might be because you are drying too big a space. Another reason could be that the humidity levels are already low. Try to close the doors or lower your setpoint for a bit.

Dehumidifier vs AC “dry” mode

Portable air conditioners in dehumidify mode can use 600 to over 1,000 watts. They might make the room feel a little warmer. If you only need to take out moisture from the air, a compressor dehumidifier uses 200 to 400 watts. This option often gets your room to the right humidity level with less energy. Use your AC’s dry mode mostly when you want some cooling or want to use its filter at the same time.

Features that reduce household costs and improve energy efficiency

• Numeric humidistat & digital readout: You can set humidity levels exactly so you don’t get too dry.
• Two fan speeds + laundry boost: Start with high speed, then switch to low. You will save kilowatt hours this way.
• Auto-restart memory: It works well with smart plugs and off-peak setups.
• Frost protection / hot-gas defrost: It has less downtime when the room gets cold.
• Washable filter & clean coils: Clean filters and coils help air move well for optimal performance.
• Quiet mode: You can use it at night without much noise. This helps with TOU rates.
• Directional louvres: Direct hot air at your racks so things dry quicker.

Placement for maximum efficiency (checklist)

• Close the doors to make a smaller space that is easy to control.
• Keep the intake and outlet open. Do not hang wet clothes over the grille.
• Aim the outlet so air goes through thick items. Turn the rack halfway during use.
• Stay away from corners where air goes right back to the intake.
• If you notice a musty smell in the room, try turning down the setting a little or add proper ventilation by opening a small gap in the window. A musty smell means there is too much trapped moisture.

Monthly cost planner (fill-in)

Model watts: Enter appliance power in watts (e.g. 120). Unit rate (p/kWh): Your tariff unit price in pence per kWh (e.g. 22.50). Hours/day ON: Actual compressor ON time per day (duty × scheduled hours).

Daily cost

£0.00

30-day cost

£0.00

If the total still feels high, you can change the duty cycle. Try closing doors, raising the setpoint from 45% up to 50–55%, or making your sessions shorter. Also, remember that you can lower every number above if you compare energy prices.

FAQs About Dehumidifier Running Costs