Life Hacks in Japan

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"Life in Japan 2023" We have found the manufacturer of the most efficient dehumidifier!

Dehumidifiers are becoming indispensable in Japan, where humidity is high throughout the year. However, dehumidifiers are largely divided into compressor and desiccant types, and there are many combinations of these types with various other functions. Let's take a closer look at dehumidifiers in order to spend comfortable days!

The basic principles are explained in an easy-to-understand manner by Dr. Denjiro Yonemura on Youtube, so I will omit it.


To examine the differences between each method, we compared products from Iris Oyama and Sharp, both of which market both compressor and desiccant types. (You can scroll to the right.)

Manufacturer Iris Oyama Iris Oyama Sharp Sharp
model number IJC-P70 IJD-K80 CV-R71 CV-R60
type Compressor type Desiccant type Compressor type Desiccant type
dehumidification capability 50Hz...5.9L / Day,
60Hz...7.3L / Day*1
8.0L / Day*2 50Hz...6.3L / Day,
60Hz...7.1L / Day*3
50Hz...5.4L / Day,
60Hz...5.6L / Day*4
Water tank capacity 2.5L 3.5L 2.5L 1.5L
Power consumption 50Hz...180W / Day,
60Hz...190W / Day
690W 50Hz...175W / Day,
60Hz...190W / Day
50Hz...480W / Day,
60Hz...540W / Day
Width 244mm 334mm 303mm 300mm
Depth 233mm 285mm 203mm 300mm
height 430mm 586mm 524mm 323mm
weight 8.3kg 9.0kg 9.4kg 6.7kg
Price*5 26,800 yen 16,465 yen - -

*1...Dehumidification volume per day (24 hours) when room temperature is maintained at 27°C and relative humidity at 60%.
*2...Dehumidification volume per day (24 hours) when room temperature is kept at 20°C and relative humidity at 60%.
*3...When dehumidification is in "high" operation. Dehumidification volume per day when room temperature is maintained at 27°C and relative humidity at 60%.
*4...During "quick dry" clothes drying operation. Dehumidification volume per day when room temperature is maintained at 20°C and relative humidity at 60%.
*5...Price on Amazon as of May 6, 2023.



Perhaps because of the difference in dehumidification capacity, the situation is reversed in the case of Iris Oyama, but generally speaking, compressor-type compressors, like Sharp's, are larger and heavier than desiccant-type compressors.

Next, regarding dehumidification capacity, as can be inferred from the different measured temperatures, the compressor type has a significant drop in dehumidification capacity when the room temperature is low, while the desiccant type has a smaller drop in dehumidification capacity.

Finally, the desiccant type uses a heater, which increases electricity costs and room temperature. Our dehumidifier is also a desiccant type, and the room temperature rose from 29°C to 32°C in August use. However, I remember that even when we were using a compressor-type dehumidifier, the room where the dehumidifier was used was getting hotter.

The differences can be summarized as follows

Dehumidification method Compressor type Desiccant type
size big small
weight heavy light
Dehumidification capacity (summer) high high
Dehumidification capacity (other than summer) low (position) high
Power consumption few large
room temperature rise small big


At first glance, you might think, "Well, the air is dry and less humid in the winter, so I don't need a dehumidifier, and wouldn't a compressor type that saves energy and doesn't raise the room temperature be better?" However, we recommend the desiccant type for two reasons.

First, let us discuss the point that "the compressor type is more energy efficient. As noted at the bottom of the table above, both Irisoyama and Sharp publish their measurement results at a room temperature of 27°C for the compressor type and 20°C for the desiccant type. One would assume that the manufacturers would want to display the dehumidification capacity as high as possible, which would mean that these temperatures have the highest dehumidification capacity. However, in Tokyo, the average temperature exceeds 25°C mainly only in July and August. (Reference...Historical Weather Data Search). Buying a compressor-type dehumidifier to save electricity for these two months will be meaningless if the dehumidification performance declines for the remaining 10 months and the inside of the house becomes moldy.

Next, regarding the "dehumidifier is not needed in winter because humidity is low", this idea is wrong in the first place. According to the data from the Japan Meteorological Agency that I referred to earlier, the average humidity was below 60% only in January and February, and even in February, the lowest month, it was 49%. The reason why humidity is high even in winter has been gaining recognition in recent years, so please refer to the following links and others for details.


There is also a hybrid type that has both properties, and some people think, "With this, I can use the compressor type for cheap in summer and the desiccant type for good dehumidification in non-summer!" Some people may think, "With this, the compressor type is cheaper in summer, and the desiccant type can dehumidify the air outside of summer! However, they are quite expensive, with prices starting at 40,000 to 55,000 yen. However, the price starts from 40,000 to 50,000 yen, and the risk of failure is also high because the structure is more complicated.

Based on the above, we recommend desiccant dehumidifiers, which consume more power but are compact and do not lose dehumidification capacity when the room temperature drops.



High dehumidification capacity

Since it is a simple mechanism, dehumidification capacity is basically proportional to the size of the unit, so you do not want to buy a high-performance but unnecessarily large unit. However, the high dehumidification capacity you need depends on the structure of your house and other factors, so you should refer to the guidelines written in the manufacturer's description. Many manufacturers provide figures based on JEMA (Japan Electrical Manufacturers' Association) standards.

Looking at the dehumidifiers sold by various manufacturers, it appears that they are being developed separately for living rooms (about 5 or 6 tatami mats if the building structure is reinforced concrete) and for living rooms (about 14 to 20 tatami mats).

Other Functions

air cleaner

The details are written in the following article, but the paper states that the results of the experiment showed that Plasmacluster/Nano-e had no sterilizing effect. Therefore, Panasonic and Sharp products with these functions are omitted from the comparison.


Humidity sensor

All manufacturers have a function to stop when the tank is full, but may not have a sensor to stop when the humidity reaches a certain value. Stopping when the humidity reaches a certain level not only saves electricity but also eliminates noise, so it is better to have one if possible. If not, you will need to adjust it yourself by using a thermo-hygrometer.


That said, there is always outside air coming inside, as evidenced by the fact that you can keep the whole house closed and not have it go sour. Also, if you leave the dehumidifier on because there is no sensor, the air will seldom dry out dry. If the humidity drops quickly, reduce the number of dehumidifiers you turn on or reduce the output itself.


The size of the tank depends on the size of the room, but it should have a handle for easy transport, as it may spill if carried fully loaded. However, if the tank is not that large, there may be no need to be overly concerned.

Louver (clothes dryer)

By adjusting the angle at which the dry air is discharged, it may be used to dry clothes, etc. Note that all of the dehumidifiers introduced next had louvers. However, since dehumidifiers are relatively heavy, it is better to use a fan or circulator to blow air instead of moving the dehumidifier, as it is easier to direct strong air over a wide area. Some products seem to have casters to make them easier to move, but I wonder, "Isn't there a risk of the humidifier falling over?" I personally think that it is a good idea.



Product Comparison Chart

Based on the above, the following table compares the following dehumidifiers

  • Desiccant type
  • No air cleaner

For living room

Manufacturer Iris Oyama
model number IJD-P20
Room Guideline
wooden...3 tatami mats (5m²),
rebar...6 tatami mats (9m²)*1
dehumidification capability 50Hz...2.4L / Day,
60Hz...2.2L / Day
Water tank capacity 2.0L
range 322mm
depth 211mm
height 464mm
weight 5.3kg
feature -
Price*2 22,800 yen

*1...Figures based on JEMA (Japan Electrical Manufacturers' Association) standards.
*2...Prices on Amazon as of May 6, 2023.


for living

Manufacturer Hitachi Siroca Iris Oyama Toyotomi
model number HJS-DR601 SDD-7D151 IJD-K80 TD-ZBS80N
Room Guideline
wooden...7 tatami mats (12m2),
rebar...14 tatami mats (23m2)*1
wooden...9 tatami mats,
rebar...18 tatami mats
wooden...10 tatami mats (17m2),
rebar...20 tatami mats (33m2)*1
wooden...10 tatami mats(17㎡),
rebar...20 tatami mats (33m2)
dehumidification capability 5.6L / Day 7.6L / Day 8.0L / Day 8.0L / Day
water tank
2.5L 2L 3.5L 4.0L
range 301mm 357mm 334mm 350mm
depth 204mm 212mm 285mm 240mm
height 502mm 553mm 586mm 506mm
weight 5.9kg 8.9kg 9.0kg 7.2kg
feature With humidity center With humidity center - Tank with handle
Price*2 19,800 yen 29,400 yen 16,465 yen -

*1...Figures based on JEMA (Japan Electrical Manufacturers' Association) standards.
*2...Prices on Amazon as of May 6, 2023.


At first, we were trying to suggest recommendations for each room based on the dehumidification capacity and room guidelines. However, perhaps due to the fact that the year of its release was as old as 2019, Hitachi's HJS-DR601 listed in the table for living rooms had a higher dehumidification capacity and a humidity sensor, despite having almost the same volume as Iris Oyama's product listed in the table for living rooms. Therefore, we recommend Hitachi's HJS-DR601 for rooms up to 7 tatami (12m2) wooden and 14 tatami (23m2) reinforced concrete. For rooms larger than that, Iris Oyama's IJD-K80, which also complies with JEMA standards, may be a good choice.

I hope the above is helpful.


See also!