I'm from the US (120V), and am interested in taking my hot air brush on my study abroad trip to Japan.

I'm aware of the voltage difference and similar plugs to the US.

The problem is that the only travel transformer I can find is (https://www.amazon.com/VCT-VT-2000J-Voltage-Converter-Transformer/dp/B004O9WIK8/ref=sr_1_1?keywords=japan+travel+transformer&qid=1556559714&s=gateway&sr=8-1) and that really seems like rolling the dice.

It has a 64% approval for 5 + 4 stars, and numerous complaints about not being well made.

Is there any reliable travel transformer that has decent ratings or a proven track record for 100V -> 120V?

  • A typical hair dryer wouldn't need a converter for such a small voltage difference especially downwards. Is there a reason you think you need one? For example, some medical devices do need a transformer but those carry heavy warnings stating so. Conversely, I never heard of anything but medical devices needing one.
    – user4188
    Commented Apr 29, 2019 at 18:35
  • No, it's a hot air brush. It's possible that it would be fine, but I'm looking to minimize the risk. Commented Apr 29, 2019 at 18:48
  • 3
    Then don't worry about it. Lower voltage can't hurt it.
    – user4188
    Commented Apr 29, 2019 at 18:49
  • 2
    It's hard to imagine that the device can suffer permanent harm from too-low voltage. But a resistive heating element designed for 120 V will only deliver 70% of its normal heat output when run at 100 V. If the brush is well made it can work fine by increasing the duty cycle to compensate, but if the maker cut corners it may have trouble keeping up. Commented Apr 29, 2019 at 21:38

3 Answers 3


You almost certainly don't need a transformer, since 100V instead of 120V is almost certainly within the tolerance of the device, particularly for a simple heating device like a hot air brush.

Fun fact: even in the US, that "120V" can actually be anything between 104V and 126V at the "utilization point" where you plug in your device.

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  • 1
    Erm, no the service entrance voltage is 114-126V as the table you inserted shows, it's utilization voltage which might drop to 104V. Check this very informative page.
    – user4188
    Commented Apr 30, 2019 at 6:17
  • So should this answer be disregarded as an assumption of it has been falsified? Commented Apr 30, 2019 at 22:20
  • @SarahSzabo No: the point remains that any electric devices you're using in the US are already capable of dealing with 100V. Commented Apr 30, 2019 at 23:05
  • @jpatokal Hmm, are you sure that the lower voltage won't cause a current surge to compensate? I've heard about voltage drop happening in very long (200') long extension cords and power equipment leading to breakers opening. Commented May 1, 2019 at 0:39
  • 1
    @SarahSzabo: One might conceivably imagine that for a device with a switch-mode power supply which (within limits) will adjust its current draw to provide the amount of power it needs at whatever voltage it gets. But for something like a hot-air brush the domiant load will be the heating element, which is purely ohmic, so lower voltage leads to lower current too. Commented May 1, 2019 at 21:27

If you don't mind something heavy, you can also find transformers for this purpose on amazon.jp. They all look like typical made-in-China adapters of dubious approvals status. Also very heavy but maybe acceptable for a long stay. The advantage is that you could order it in-country if your gadget does not work properly.

If your Japanese is good enough to deal with their site, try searching for "昇降圧兼用 変圧器". Some of the reviews are bad because they are trying to use devices with high surge currents such as compressors or refrigerators, which your device should not be.

  • If you are going to buy a transformer, it's probably as cheap to just buy a new hot air brush. Commented Apr 30, 2019 at 9:33
  • That's what I was considering. I have a DSI which charges at 120V (Not 100-120) and I wouldn't want to risk damaging the lithium ion battery (Which may fail catastrophically). I've found a similar 100V @50Hz (I'm in a 50Hz region) hot air brush just like the one I have. Commented Apr 30, 2019 at 21:23

You are most likely not going to find a suitable consumer-targeted transformer to go from 100 to 120 V with their respective tolerances. Most devices that people are likely to take with them on a trip from Japan to North America or vice-versa are well-suited to handle both nominal 100 V and nominal 120 V. While there is a (small) market for 100/120 V to 230/240 V transformers to go to or from the European standard from the Japanese/North American one the average consumer will not need any transformation from 100 V to 120 V.

On the other hand, Japan has a very big market for consumer electronic devices so if you have any doubts about your hot air brush not being able to handle slightly lower Japanese voltage I would suggest just buying a new one in Japan.

Japan also has a well-developed second-hand market so you may well be able to sell it off for a good price when you leave, assuming it’s still in good condition.

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