How much does a dehumidifier cost to run in NZ?

About $40 a month for a 600W unit run six hours a night, which is the typical winter pattern. Left running around the clock it is closer to $159 a month. Most units cycle rather than drawing full power continuously, so real figures often land 20-30% below these.

Does a dehumidifier heat the room?

A little, and not on purpose. Almost all the electricity a dehumidifier uses ends up as heat in the room, plus a small amount released when water vapour condenses - so a 600W unit warms a room roughly like a 600W heater. That is a genuinely inefficient way to heat, but it is not wasted either: dry air is cheaper to heat than damp air and feels warmer at the same temperature, so a dehumidifier can slightly reduce what your actual heater has to do.

Compressor or desiccant dehumidifier for a New Zealand winter?

Desiccant, if the room gets genuinely cold. Compressor units work by condensing moisture on a cold coil, and their capacity falls away below about 15°C - which is precisely the condition a damp New Zealand bedroom is in when you need it most. Desiccant units keep working down to near freezing. They draw a bit more power for the same water removed, but a compressor unit that has stopped pulling water is drawing power for nothing at all.

Is it cheaper to open the windows than run a dehumidifier?

Often, yes - and it is the first thing to try. On a dry day, cross-ventilating for fifteen or twenty minutes dumps a lot of indoor moisture for no cost whatsoever. Ventilation loses to a dehumidifier when the outside air is wetter than the inside air, which in much of New Zealand means long damp spells rather than cold snaps. The two are complements: ventilate when the outside air is dry, dehumidify when it is not.

Running cost

What a dehumidifier costs to run in a NZ home

By Jason Webb· Published 6 August 2026· Updated 6 August 2026· 7 min read

Dehumidifiers are close to a New Zealand household appliance in a way they are not in most countries. BRANZ survey work has repeatedly found damp and visible mould across a large share of the housing stock, and a dehumidifier is the appliance people buy when a bedroom wall starts growing something.

A typical unit draws about 600W - between a fan heater and a fridge - and costs roughly $40 a month run six hours a night through winter.

Cost by how you run it

Monthly and per-winter cost of a 600W dehumidifier at 36.3c/kWh
Pattern	Per month	Across a 3-month winter
2 hours - overnight in one bedroom	$13	$40
6 hours - a damp room, most of a night	$40	$119
12 hours - continuous while the house is empty	$80	$239
24 hours - left running permanently	$159	$477

Treat those as upper bounds. Any unit with a humidistat switches off once it reaches the target humidity and only restarts when the room drifts back up, so a well-set unit in a room that is not hopelessly damp may only run half the hours you set it for. A unit that genuinely runs flat out for twelve hours a day is telling you something about the room rather than about the appliance.

Compressor or desiccant - it matters more here than elsewhere

This is the decision that most affects whether you get value, and it hinges on a detail of how each type works.

A compressor unit condenses moisture onto a cold coil, exactly like a fridge. That works well in a warm room. As the air gets colder, the coil has less of a temperature advantage to work with and capacity falls away - by around 15°C it is noticeably struggling, and below 10°C many units achieve very little while still drawing power.

A desiccant unit passes air over a moisture-absorbing wheel and then drives the water off with a heater. It does not care how cold the room is, and keeps working down towards freezing.

Running six hours a night, by dehumidifier type
Type	Typical draw	Per month	Cold-weather behaviour
Compressor (refrigerant)	600W	$40	Efficient above ~15°C, drops off sharply below
Desiccant	700W	$46	Works down to ~1°C, draws more but keeps pulling water

The desiccant unit costs a little more to run - but the relevant comparison is not cost per hour, it is cost per litre of water removed. In an unheated New Zealand bedroom at 12°C in July, a compressor unit can be the more expensive of the two despite the lower wattage, because it is pulling out far less water for the power it draws.

It is not a heater, but it is not nothing either

People often notice a room feels warmer with the dehumidifier running and conclude they have found free heat. What is happening is real but modest: essentially all the electricity the unit uses ends up as heat in the room, plus a small additional amount released as water vapour condenses back to liquid.

So a 600W dehumidifier warms a room about as much as a 600W heater - which is to say, it is a poor heater, because resistive heating is a poor way to warm a room and this is resistive heating with extra steps.

The genuine benefit is indirect. Dry air holds less heat than damp air, so it takes less energy to warm, and at the same temperature it feels warmer. Getting the humidity down means your actual heater runs less and you are comfortable at a lower thermostat setting. That is a real saving, it just does not show up as the dehumidifier being cheap.

Try ventilation first - it is free

Before buying or running anything, it is worth knowing where the moisture comes from. In most New Zealand homes it is generated indoors: showering, cooking, drying laundry on racks, and simply breathing - a household of four puts several litres of water into the air every day.

The cheapest response to indoor-generated moisture is to put it back outside:

Cross-ventilate on dry days. Windows on opposite sides of the house for fifteen to twenty minutes shifts a surprising volume of moist air, at no cost.
Extract at source. A bathroom fan that vents outside, and a rangehood that does the same, remove water vapour before it reaches the rest of the house. A fan venting into the ceiling cavity is moving the problem, not solving it.
Stop drying laundry indoors if there is any alternative. A single load on an indoor rack releases a couple of litres of water into the house.
Check for a ground-moisture source. A polythene vapour barrier under a suspended floor is a one-off job that can transform a persistently damp house, and no dehumidifier will out-run a wet subfloor.

A dehumidifier earns its place when the outside air is wetter than the inside air - long damp spells rather than crisp cold ones - and in rooms that cannot be effectively ventilated. Used that way, the figures in the first table are good value against the cost of mould damage and the health consequences that come with it.

To price your own unit and schedule, open the calculator. Our guide on dehumidifier versus heat pump works through which of the two to reach for when a room is both cold and damp - which in New Zealand it usually is.