The real cost of a humidifier
depends on
your heater.

Costs come from each maker's published power use and output, at ¥31/kWh. "Per liter" is what the unit itself costs to put 1 liter of water into the air.

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Ultrasonic models are cheap and quiet, but they spray the tank water straight into the room. Only for people who won't skip the cleaning!

Evaporating water takes heat: about 0.68 kWh per liter (from the heat of vaporization of water at 20°C, about 2,450 kJ/kg). Where that heat comes from is what separates the types.

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A steam humidifier pays for all of that heat with electricity, which is why it costs more to run. Evaporative and ultrasonic types use little power themselves, but they borrow heat from the room air to evaporate the water, and your heater makes up for it.

If that heater is an electric or oil heater, 1 kWh of electricity gives 1 kWh of heat. Either way you end up paying for about 0.68 kWh per liter in electricity, so the totals come out almost the same. An air conditioner moves several times more heat than the electricity it uses, so the evaporative type, which borrows room heat, works out cheaper.

Professor Plug: every watt a humidifier uses ends up as heat in your room too. So the fair comparison is the unit's own cost plus what your heater has to make up.

Japan's Ministry of Health, Labour and Welfare warns that humidifiers can spread Legionella bacteria, and says to change the water every day and wash the container for ultrasonic and similar types. Because Legionella is killed in 5 minutes at 60°C, it says types that heat water to make steam are unlikely to be a source of infection.

Choosing only on running cost often leads to cleaning regrets. Ask yourself first: will I really wash it every day?

1. Read the room size for a "wooden Japanese-style room"

   Humidifiers list two sizes, such as "木造和室 9 tatami / プレハブ洋室 15 tatami". Under the industry standard (JEM1426), the wooden-room figure is the smaller one. When in doubt, match that smaller figure to your room (1 tatami ≈ 1.6 m²).

2. Get one with a humidity sensor and auto mode

   Turning output down automatically at your set humidity prevents over-humidifying and cuts the bill. Our calculator assumes full output, so real costs are lower.

3. Check tank size and continuous run time

   The Sharp HV-T55 (about 4.0 L tank), for example, runs about 7.2 hours on high and about 19 hours on quiet. If you'll use it overnight, make sure it won't run dry.

4. Easy to clean

   Can you get your hand inside the tank? Do the filter and tray come out for washing? For evaporative and hybrid types, also check how often the filter needs replacing and what it costs.

5. Decide where it goes first

   Steam outlets get hot, so keep them out of reach of children and pets. Near a window it can cause condensation; the middle of the room is better.

1. Search in Japanese

   Humidifier is 加湿器. Steam type is スチーム式, evaporative is 気化式, ultrasonic is 超音波式, hybrid is ハイブリッド式. Room size is 適用床面積 or 適用畳数.

2. Buy a model made for Japan

   Household power here is 100V. Overseas models may not be designed for it, so choose one sold for the Japanese market.

3. Manuals are usually in Japanese

   Cleaning steps and filter replacement times are in the manual. A phone translation app works well on the cleaning pages.

4. Your electricity rate may differ

   We use ¥31/kWh, the industry guideline. Your actual rate depends on your plan and power company.