Most consumer electronic devices these days use switched-mode power supplies, which typically specify they can take input power between 100–240 V, at frequencies of 50–60 Hz AC. All my typical travel devices (phone, camera, laptop chargers) have these ranges, and with a universal plug/adapter (i.e. just a physical adaptor, no transformer) you can then plug them in pretty much anywhere.

But are there any countries with mains power outside this range? Is there anywhere that I need to be careful about or avoid using such devices? Or does the range completely cover all countries' mains power supplies?

I would hope (and am assuming) that the range is designed to cover everywhere in the world with mains power, but can imagine if one or two small countries were outside this range (e.g. 50V or 300V, or 100 Hz), it may not be worth the effort of all devices supporting them.

  • 5 years on :-) - Some specialist areas have unusual supplies. Some aircraft supplies were/are 400 Hz. Not a V or F issue, but, Shipboard supplies tend to float BOTH legs relative to the hull. If either is hard hull connected it indicates a fault which is liable to be a problem in an 'earth all over the place' environment, so such fauts are sought out "with malice a fore thought". Commented Jan 16, 2019 at 12:15

5 Answers 5


All "normal" mains power supplies should be OK. Most 'universal' supplies will work down to 90 VAC. Most switch mode supplies convert the AC to DC and then deal with that.

You can find exotic systems - but not in normal use. Maybe shipboard or aircraft in extreme cases - but nothing that they would supply to members of the public.

Rarely in "out of the way" places you may encounter non-standard supplies that could cause problems - usually at remote or isolated locations. Usually where connection to a national grid is not available and power is produced locally. Examples might be diesel or LPG (usually) powered alternators, and low voltage to mains supplies using electronic inverters.

Even in such situations larger alternator systems usually produce properly regulated voltages. Frequency may wander somewhat during large loads or load variations. Voltages may be low under heavy loading.

"Bottom end" electronic inverters may produce quasi-sine-wave outputs - rather than providing a sine wave the output goes 0, +V, 0, -V, 0 ... with the on to off ratio adjusted to provide an approximation to mains AC for most equipment. Some power supplied (laptops, some PCs, others) may be damaged by applying these step waveforms due to input filter capacitors. (I have heard power supplies which buzz loudly in such cases. Some few systems may see these as too high or too low in voltage.)

  • The one thing you need to be careful of are switch mode power supplies with two ranges that switch between two ranges (eg 90-150, and 170-270) usually for efficency's sake, and countries with 220/230/240V AC and frequent brown outs. Eventually your power supply will end up deciding it's running at 110V engage its voltage doubler and then be horrifically surprised by 230V and go bang. Nigeria is a good example.
    – james
    Commented Jan 14, 2019 at 22:16
  • @james Yes. I've seen it happen here in NZ, where power quality is generally reasonable. Commented Jan 16, 2019 at 12:11

According to Wikipedia, the minimal voltage is 100 V in Japan and the maximum voltage 240 V in several countries. As for the frequency, they all lie between 50-60 Hz. So there isn't any country with such an exotic voltage or frequency that wouldn't fit the range you mentioned.

If you think of it, it wouldn't make sense for a small country to go too far outside the two common voltages, as that would mean that you'd have to produce a range of electric devices just for that one country.

  • 1
    Unless the small country made the decision way back in the early days of electricity and is very stubborn / closed off from the rest of the world. Something like a North Korea perhaps... Commented Jan 25, 2014 at 15:30
  • 1
    @hippietrail though not the actual North Korea, which was electrified under Japanese rule. Commented Jan 23, 2018 at 10:10

"Universal" supplies are just that

Utility power available to general consumers and travellers is going to be in the 85-265VAC/47-63Hz range that your average "universal input" SMPS is rated for. Reputable (read: listed) supplies are tested to every corner of this range (although some are only rated to 90VAC min).

Not having a grid isn't a problem either

Modified square waves (+peak, 0, -peak, 0, +peak) shouldn't be an issue -- the only potential problem is with active Power Factor Correction circuits misbehaving in mild ways (such as not providing proper PFC, or emitting undesired audible noises). (Keep in mind that just about all consumer standby power supplies and many low-end inverters generate MSW output.) Likewise, wandering frequency (from a generator) won't harm the supply much if at all -- the PFC circuit generally has enough bandwidth to track a source that drifts.

Noise filtering is a necessity on SMPSes anyway, so they generally reject external noise. Spikes are sometimes suppressed by a metal-oxide varistor or MOV (same thing you'd find in a surge strip), but are probably the greatest hazard unstable power can pose to a modern SMPS.

Weird and wild power sources

DC, interestingly enough, provided the voltage is reasonable (locomotive auxiliary ~70VDC is pushing it, but say a 115VDC or even a 380VDC rail should be OK), isn't an issue. In this case, the PFC circuit, if present, simply acts as a straight boost converter, and the input diodes do (almost) nothing.

Likewise, 400Hz aircraft/marine power sources won't cause much trouble either, although supplies listed for such use are generally only seen on more specialized gear, such as test equipment. Most input diodes can deal with it, and most PFC circuits have the bandwidth to roughly follow a 400Hz sine, albeit with degraded performance.

This leaves one more oddball to cover, and it hails not from some out of the way place, but North American industry. It's the 277V/60Hz single phase power sometimes found there, and it probably comes the closest you'll ever see to thwarting the universal-ness of your supply -- a reputable universal supply will start up and run on it, but with reduced margin for surges as the peak DC bus voltage is around 390V vs 340V for 240V mains in. Thankfully, 277V is rare to see at a receptacle even in large buildings in the US, and you wouldn't be able to plug a normal North American NEMA 5 plug into it anyway! (277V single phase uses the NEMA 7 receptacle.)

  • "Noise filtering is a necessity on SMPSes anyway, so they generally reject external noise." The problem is they put capacitors across the supply to filter out noise. A waveform with high frequency components or a higher fundamental frequency will substantially increase the current in those capacitors. If they are marginal to start with then this may be a problem. Commented Apr 29, 2018 at 2:42

The most unusual power supply that I have encountered is the Philippines: 220V (or maybe 230V, I forget) 60Hz. So, a European / most of the world style voltage but a North American style frequency. This used to cause an issue with some of the larger computers and the hardware engineers would complain about it. However, most modern consumer electronic devices are quite happy there.

Further trouble is caused by their use of North American style sockets. So, US devices will fit and appear to be suitable but will often go bang when used. This will still be probable for many simpler devices e.g. light bulbs, hair driers, etc. Most electronic gadgets now accept a wide range of supplies but don't assume that all devices do.

If you are going to quite out of the way places then you may want to consider the quality of the supply. The nominal voltage may be suitable but there could be nasty spikes. You might want to research protection against that.


According to Wikipedia (in New York City): In January 1998, Consolidated Edison started to eliminate DC service. At that time there were 4,600 DC customers. By 2006, there were only 60 customers using DC service, and on November 14, 2007, the last direct-current distribution by Con Edison was shut down.

That means the last place that used DC current discribution was definitely eliminated in 2007. Never mind voltage and frequency differences, plugging your average power adapter into DC could be catastrophic (especially if there is a transformer involved). But I guess there were no "publicly" accessible sockets years before that.

Note that there are still special purpose DC sockets used from place to place (mostly 48V), but fortunately all of them should be incompatible with the "common" A/C mains plugs.

  • There is one common place where a DC socket is available to the public: your car - 12V DC. But that's obviously a very different adapter Commented Jan 23, 2018 at 10:16

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