Using a dehumidifier to dry laundry

Indoor drying in a British winter puts water into the room. Cold glass then collects it. A dehumidifier does not heat the clothes the way a tumble dryer does. It runs a compressor, condenses moisture out of the air, and collects that water in a tank. People put it in a closed room with an airer, use a laundry setting, and let it switch itself off. The electricity cost is the compressor and the fan, for however long they actually run.

The six-hour laundry mode

The 12-litre model linked below has a laundry mode aimed at drying washing. The instruction manual says the mode targets a low humidity, runs the fan on high, and turns the machine off after six hours. If the room gets very dry before that, the compressor pauses and the fan can continue. So “six hours” is the timer, not a guarantee that the compressor draws full power for every minute.

The maker’s product page gives a running-cost example of about 4p an hour based on 26.32p/kWh. Divide those two numbers and the implied power is 4 ÷ 26.32 × 1,000 = 152W. Across a full six-hour timer that is 0.152 × 6 = 0.91 kWh. Cost that both ways:

• Off-peak: 0.91 × 7.6p = 6.9p.
• Cap rate: 0.91 × 26.32p = 24.0p, which is also 6 × 4p.

If the compressor pauses, the real session uses less than 0.91 kWh. The 4p example is the maker’s illustration at the cap rate, not a meter reading from your room. An Amazon specification line for the same series has also shown a lower wattage. Where two published figures disagree, this page uses the maker’s own pence-per-hour example and shows the division, rather than picking a third number.

Why the calculator says 0.8 kWh

The homepage laundry tab uses 0.8 kWh per dehumidifier session so one slider can be compared with a 1.4 kWh heat-pump assumption and a 3.1 kWh condenser assumption. 0.8 kWh is 6.1p at 7.6p/kWh and 21.1p at 26.32p/kWh. It is a round comparison figure, a little under the six-hour, 152W illustration. If you want the maker’s example, use 0.91 kWh. If you want the chart on the homepage, use 0.8 kWh and the calculator. Do not add them together.

Five sessions a week is 260 sessions a year. At 0.91 kWh that is 237 kWh: £18.00 at 7.6p, or £62.30 at 26.32p. The same year of heat-pump cycles at the site’s 1.4 kWh assumption would be 364 kWh if you also did five a week, which is more electricity than the dehumidifier illustration. The dryer finishes a load without the airer. The dehumidifier session is the cheaper electricity on these assumptions, and it is the one that takes water out of the room air.

Using the cheap window

A laundry mode that runs for a fixed six hours lines up with Intelligent Octopus Go’s 23:30–05:30 window. Start it at 23:30 and the timer ends as the cheap period ends. A plug with a schedule can do that switch-on if you do not want to wait up. The plug has to be rated for the load. A dehumidifier around 150W is a normal small-appliance load. Do not use that as permission to switch a tumble dryer through the same plug.

The water tank still needs emptying, and the room needs to be shut or the machine is drying the landing as well as the washing. Those are practical limits, not electricity maths. The standing charge is also outside this sum. 54.83p a day is about £200 a year whether or not you run a drying session.

Shelf price is not estimated here. The card on the homepage names the model; this guide keeps to the job it does and the pence per session.

Sources

• Ofgem, price cap 1 October–31 December 2026
• Ofgem, unit rates and standing charges
• Octopus Energy, Intelligent Octopus Go
• Meaco, Arete One 12L (published running-cost example)
• MeacoDry Arete One 10/12L manual, laundry mode
• Lakeland, Dry:Soon family specifications (Mini, 198W)

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