Quick answer: a dehumidifier’s running cost depends on its wattage, how long it operates and your electricity unit rate. Use the calculator below for a quick estimate, then measure real kWh use for a more accurate result. At the illustrative rate of 26.11p per kWh, a 300W model costs about 7.8p per hour, 63p for eight hours, or £18.80 for 30 days at eight hours a day—if it runs continuously at its full rated power.
Dehumidifier running-cost calculator
Enter the appliance’s rated power, how long it runs, and the unit rate from your bill. This estimates the extra electricity cost; it does not add the daily standing charge.
Estimated cost per hour: £0.00
Estimated cost per day: £0.00
Estimated cost for 30 days: £0.00
Estimated electricity used for the period: 0.00 kWh
Estimate assumes the dehumidifier draws its rated power for every hour entered. Many units cycle on and off once the target humidity is reached.
Last checked: 25 September 2026. The example unit rate below is the Ofgem average electricity unit rate for a standard-variable-tariff customer paying by Direct Debit in England, Scotland and Wales between 1 July and 30 September 2026. Your tariff, payment method, meter type and region can differ. Check your bill for your actual rate before relying on any figure. Ofgem’s current unit-rate information.
Dehumidifier running cost calculation
Use this formula:
Cost (£) = watts ÷ 1,000 × hours used × unit rate (£/kWh)
A 300W appliance is 0.3kW. If it runs at full power for eight hours at 26.11p per kWh:
0.3 × 8 × £0.2611 = £0.62664
That is about 63p. For a 30-day month at the same usage, it would be approximately £18.80.
Dehumidifier cost per hour, day and month
The table assumes continuous full-power operation and an illustrative electricity unit rate of 26.11p/kWh. It shows the additional electricity cost of using the appliance, not your whole bill.
| Rated power | Per hour | Eight hours | Per day (24 hours) | 30 days at eight hours/day |
|---|---|---|---|---|
| 200W | 5.2p | 41.8p | £1.25 | £12.53 |
| 300W | 7.8p | 62.7p | £1.88 | £18.80 |
| 400W | 10.4p | 83.6p | £2.51 | £25.07 |
| 500W | 13.1p | £1.04 | £3.13 | £31.33 |
| 600W | 15.7p | £1.25 | £3.76 | £37.60 |
These are not promises of what your model will cost. A dehumidifier may draw less than its label rating for part of the day, or it may not run its compressor/heater continuously once it reaches the set humidity.
Use your unit rate, not the standing charge
Your bill has two separate electricity costs:
- Unit rate: the price per kilowatt hour (kWh) of electricity used. This is the figure that changes when you run a dehumidifier.
- Standing charge: a fixed daily charge. You normally pay it even on a day when you use no electricity, so it should not be added again to calculate an appliance’s incremental running cost.
Ofgem explains that suppliers set a tariff’s unit rate and daily standing charge, while the price cap limits the maximum rates on eligible default tariffs; it does not limit a household’s total bill. Read Ofgem’s explanation.
Why your real cost may differ
Wattage is a useful starting point, but it is not always the same as average consumption.
- Humidistat cycling: once a room reaches the humidity you set, a compressor model may pause and restart later. The average cost can therefore be lower than a full-power calculation.
- Mode selected: laundry, continuous, turbo and drying modes can make an appliance run harder or for longer.
- Room conditions: temperature, starting humidity, ventilation, room size and how often doors are opened all affect operating time.
- Technology: compressor and desiccant dehumidifiers use electricity differently. Do not assume one will always cost less without checking the model’s rated input power and how it will be used.
- Rated extraction is not wattage: a “12L” or “20L” label generally refers to water-extraction capacity under stated test conditions. It is not the number to use in an electricity-cost calculation.
How to measure dehumidifier electricity use
For a real-world result, measure the appliance over several ordinary days rather than guessing from its label.
- Plug the dehumidifier directly into a UK Type G energy-monitoring smart plug or plug-in electricity meter that is rated for the appliance’s maximum load.
- Reset the meter, then use the dehumidifier normally for at least 24 hours; a week is better if humidity changes a lot.
- Record the total kWh used.
- Multiply those kWh by the unit rate on your electricity bill.
For example, if your meter reports 4.2kWh over three days and your rate is 26.11p/kWh, the appliance cost about £1.10 over that period. This approach includes compressor cycling and is usually more useful than multiplying the maximum wattage by every hour it was plugged in.
Do not use an extension lead merely to make a meter reach the appliance. Follow the dehumidifier and meter manufacturers’ instructions, keep electrical connections dry, and check that the monitor is rated for the load.
Compare UK smart plugs with energy monitoring →Compressor or desiccant: which costs less?
There is no universal winner. Compare the exact models and your room conditions.
| Factor | Compressor dehumidifier | Desiccant dehumidifier |
|---|---|---|
| Electricity use | Often has a lower rated input power for comparable domestic models, but varies by model | Often has a higher rated input power because it uses a heating element, but varies by model |
| Cooler rooms | Can be less effective in colder spaces | Often chosen for cooler spaces because of the technology’s operating characteristics |
| Best comparison method | Compare the rated input power and measure actual kWh | Compare the rated input power and measure actual kWh |
Choose based on moisture-removal performance, room temperature, noise, drainage options and measured energy use—not a broad claim that one type is always cheapest.
Using a dehumidifier to dry laundry
Using a dehumidifier to dry clothes indoors is one of the most common reasons UK households buy one, particularly in autumn and winter when outdoor drying is impractical. Martin Lewis, the consumer finance campaigner, has repeatedly highlighted dehumidifiers as a cheaper alternative to tumble dryers for drying laundry, which has contributed to significant public interest in the topic.
How it works: a dehumidifier removes moisture from the air, which speeds up evaporation from wet clothes hung on a rack or rail. You do not place clothes inside the dehumidifier — it works by drying the surrounding air.
Cost comparison with a tumble dryer: a typical condenser tumble dryer uses roughly 4.5–5.5 kWh per cycle, costing about £1.18–£1.44 at 26.11p/kWh . A 250W dehumidifier running for six hours uses about 1.5 kWh, costing roughly 39p — a fraction of the tumble dryer cost. Actual costs depend on load size, fabric type and how long the clothes take to dry.
Tips for drying laundry with a dehumidifier:
- Place the dehumidifier close to the clothes rack or hanging rail.
- Keep the room door and windows closed to contain the moisture.
- Use a fan on the opposite side of the room to circulate air and speed up evaporation.
- Select the dehumidifier’s laundry mode if it has one — it typically runs the fan at maximum speed.
- Do not drape clothes directly over the dehumidifier, as this can block airflow and pose a safety risk.
This approach takes longer than a tumble dryer and requires a clothes rack, but the electricity savings can be significant over a drying season.
Ways to control cost without ignoring damp
A dehumidifier can be useful for drying laundry, condensation or moisture control. The aim should be to avoid unnecessary run time, not to leave a damp problem untreated.
- Use the built-in humidistat where available rather than running continuously without a target.
- Keep external doors and windows closed while the dehumidifier is working, unless you are deliberately ventilating for another reason.
- Close internal doors if you are drying one room rather than the whole home.
- Clean filters and maintain the appliance according to its manual.
- Empty the tank promptly or use a safe, manufacturer-approved drainage arrangement where suitable.
- Measure first: check whether a lower setting or shorter schedule still achieves the humidity level you need.
If you have persistent mould, leaks, penetrating damp, serious condensation or concerns about ventilation, a dehumidifier may manage symptoms but not solve the underlying cause. Renters should document the issue and report it to the landlord or managing agent.
Frequently asked questions
How much does a 300W dehumidifier cost to run?
At 26.11p/kWh, a 300W appliance costs about 7.8p per hour at full power. It costs roughly 63p for eight hours and £18.80 for 30 days at eight hours a day. Enter your own unit rate in the calculator for a personal estimate.
How much does a dehumidifier cost to run overnight?
Multiply the appliance’s kilowatt rating by the number of overnight hours and your unit rate. For example, a 300W dehumidifier used for eight hours at 26.11p/kWh is about 63p if it stays at full power. Its real cost may be lower if it cycles off after reaching its target humidity.
Does a dehumidifier use a lot of electricity?
It depends on its rated power and duty cycle. A 300W unit uses 0.3kWh for every hour it actually operates at 300W. A plug-in meter or energy-monitoring smart plug can show the real kWh used in your home.
Does a 20L dehumidifier cost more to run?
Not automatically. The “20L” figure is usually an extraction rating, not a power rating. Check the model’s wattage or rated input power, then calculate from that figure. Compare like-for-like usage and measure the actual kWh if running cost is important.
Do I include the daily standing charge?
No, not when calculating the extra cost of using this appliance. The standing charge is normally paid regardless of whether the dehumidifier runs. Use the electricity unit rate for the appliance calculation.
Is it cheaper to run a dehumidifier or a tumble dryer?
Yes. A dehumidifier is usually cheaper to run than a tumble dryer. A typical compressor dehumidifier costs around 5–8p per hour, while a tumble dryer can cost approximately 60p–£1 or more per hour, depending on the model and electricity tariff.
Can you use a dehumidifier to dry clothes?
Yes. Place the clothes on an indoor airer in a small, closed room and run the dehumidifier nearby. Keeping the door and windows closed helps the machine remove moisture more efficiently. It may take several hours, but it uses less electricity and is gentler on clothes than a tumble dryer.
How much does it cost to dry clothes with a dehumidifier?
Drying one load typically costs around 30p–70p, depending on the dehumidifier’s wattage, drying time and your electricity rate. For example, a 200W dehumidifier running for six hours at 28p per kWh would cost about 34p. A tumble dryer can cost roughly £1 or more for a similar load.
Related guides
- How to measure an appliance's electricity use →
- Electricity unit rates and standing charges explained →
- Best smart plugs with energy monitoring for UK homes →
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