-->Japan's invisible electric wall

Japan's invisible electric wall<br>7 min read May 9, 2026

Looking for vintage clocks

Japan’s mains electricity<br>comes in two different frequencies with half of the country using 50 Hz and the<br>other 60 Hz.

I stumbled onto this while shopping for vintage desk clocks on eBay. I already<br>knew about the voltage difference — Japan runs on 100 V, the US on 120 V,<br>same-looking plugs notwithstanding. Back when I tried to buy a<br>Muji toaster oven, I stumbled upon reviews of the brave<br>souls who learned the hard way why you shouldn’t import one. They talked about<br>how the low setting was pretty much high, and the highest setting would<br>immediately burn its contents.

This isn’t a problem with most low-power electronics, since they use USB-C or a<br>power brick that supports a wide range of frequencies and voltages and converts<br>it to the right DC voltage. So while I was looking for clocks, I found plenty<br>that would work in the US, like this Copal 222 that can do anywhere from 80 to<br>120 V at 60 Hz.

But then I noticed something weird. First up is this Seiko flip clock shaped<br>like a wooden ball. On the back it says it takes 100 V at 50 Hz, with a warning<br>to check the mains frequency when using it.

Then I find another Seiko flip clock with a switch on the back between 50 Hz and<br>60 Hz. Is that switch for using in a different country?

I remember in older PC power supplies there was often<br>a switch between 120 V and 240 V,<br>but I don’t remember seeing a switch for the frequency.

The electric wall

I looked at the<br>table of mains voltages, frequencies, and plugs<br>on Wikipedia and discovered that not only is Japan the only country that uses<br>100 V, but that its supply frequency is both 50 Hz and 60 Hz.

I became more curious when I looked at a map of Japan and noticed that the<br>western half uses 60 Hz while the eastern half is on 50 Hz, with a border in the<br>middle where some places seem to use both.

Marveling at railfans’ maps

Coincidentally, I bumped into the invisible wall again when I was browsing<br>OpenRailwayMap, a collaborative project based<br>on OpenStreetMap technology aimed at mapping railroad lines worldwide. Looking<br>around Japan, I noticed a couple of things.

If you follow the<br>Tōkaidō Shinkansen (bullet<br>train) from Tokyo towards Osaka, you’ll notice all the conventional rail lines<br>that generally use DC power. But you’ll also see the<br>New Transit Yurikamome running<br>nearby — and that one runs on 50 Hz, while the Tōkaidō Shinkansen runs on 60 Hz.<br>50 Hz is expected, since that’s the mains frequency in Tokyo.

Tōkaidō Shinkansen in red and<br>New Transit Yurikamome in light green

You see, when the first Shinkansen was constructed, given that most of the route<br>was in the 60 Hz section of the country, the portions that fell in the 50 Hz<br>section had frequency conversion<br>substations installed to standardize<br>the entire line at 60 Hz.[1] They’ve<br>continued to upgrade these converters for efficiency and reliability till today.

Tōkaidō Shinkansen route in<br>red

But the 50 Hz/60 Hz divide doesn’t stop with the Tōkaidō Shinkansen. It gets<br>more interesting with the<br>Hokuriku Shinkansen, which<br>we recently took from Tokyo to Kanazawa. When that line<br>opened in 1997, it was known as the Nagano Shinkansen — helpful since it<br>terminated in Nagano and would take tourists to the Nagano Olympics. It was the<br>first Shinkansen to have trains (the<br>E2 series) capable of<br>operating on both 50 Hz and 60 Hz overhead lines because reaching Nagano<br>required crossing that boundary.<br>E4 double-deckers were<br>later added to the line, also equipped for both frequencies.

E4, left and E2, right<br>(ykanazawa1999<br>on Flickr)

When the extension to Kanazawa was completed in 2014, the line was renamed to<br>its original intended name: the Hokuriku Shinkansen. The full route crossed the<br>frequency border three times, meaning the new<br>E7/W7 trains also<br>carry dual-frequency equipment like the E2 and E4 before them.

Hokuriku Shinkansen route in<br>red

How did Japan get here?

So there’s this wall down the middle of Japan, but how did it get there?

The first large electric generators in Japan were purchased by the Tokyo<br>Electric Light Company around 1895–96 and supplied by<br>AEG.[2] A year or two later, they<br>bought more from Siemens. All of these German generators operated on three-phase<br>AC at 50 Hz. But a competing company, the Osaka Electric Light Company,<br>purchased generators from General Electric, which operated at 60 Hz. Though the<br>system was small at the time, there was already fragmentation between Japan’s<br>two largest cities.

Vintage postcard of a substation<br>(Edo Tokyo<br>Museum)

Over the following decades, more electric companies sprung up and purchased<br>their own generators. In 1939, during World War II, the Japanese government<br>established the Japan Electric Generation and Transmission Company to control<br>electricity generation and transmission — mainly to eliminate overlapping<br>facilities and competition. They consolidated the commercial frequency: 50 Hz...