The vast majority of countries use ~240-volt mains electricity, although a few early adopters (such as the United States and Japan) still use ~120-volt mains electricity. 240-volt power has the advantage of having lower resistive losses than 120-volt power, and, thus, not requiring conductors as large as those found in 120-volt countries; however, countries that electrified early, when 120 volts was still the only game in town, are stuck with their lower mains voltage because switching to 240 volts would be too much trouble.

Since using even-higher-voltage mains power would decrease losses still further, why don't any countries use 360-volt, 480-volt, 600-volt, or greater household mains power?*

*Partial exception: 240/400-volt three-phase mains power is apparently somewhat common in northern Europe, but my question isn't about three-phase power.

  • \$\begingroup\$ What would be the point in changing? \$\endgroup\$
    – Chu
    Jun 20, 2018 at 22:47
  • \$\begingroup\$ @Chu: I wasn't talking about changing (in fact, my question specifically points out why changing an already-electrified country's mains voltage would be more trouble than it would be worth), but, rather, why no country adopted a mains voltage higher than 240 volts when electrifying. \$\endgroup\$
    – Vikki
    Jun 20, 2018 at 22:49
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    \$\begingroup\$ 120 VAC is a shock hazard by itself. Each time you double that voltage that wattage through a persons body would quadruple. 480 VAC would be 16 times as dangerous as 120 VAC. The fact that motors and other devices are more efficient at higher voltages is not worth the risk. \$\endgroup\$
    – user105652
    Jun 21, 2018 at 1:41
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    \$\begingroup\$ Residential supply in Seitzerland is standard with 3phase, in UK you can pay a fee and have 3phase installed if you wish to run a big welder etc.. \$\endgroup\$
    – Solar Mike
    Jun 21, 2018 at 4:20
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    \$\begingroup\$ @dandavis: Actually, in Europe they're not that unusual. In particular, 400V electric stoves aren't that exceptional. Three phase, of course. \$\endgroup\$
    – MSalters
    Jun 21, 2018 at 11:50

5 Answers 5


Japan is a bit of an exception- they adopted 100/200VAC for residential power rather than 120/240VAC. As with North America, the higher voltage is not typically present on sockets all over the place, but is wired specifically for high power consumption appliances such as central air conditioners. If you buy a house with a gas range, there will probably be a 240VAC circuit roughed in, just in case you want to go electric.

As far as I can tell (via Wikipedia and their references), the 120V nucleated from the US in the 1880s. The present 3-wire system (120/240, previously a bit less) was introduced in the 1880s as well.

Starting with one utility in Germany, the mains voltage was doubled to 220V, and the European standard spread from there. As to why not 300 or 480V, safety would be the answer. Early systems were at the same voltage as earlier DC systems, which would have been more dangerous than AC for the same voltage. So now we have North American homes wired with 120VAC to most wall outlets and major appliances typically get 240VAC (or 208 in apartment buildings because of 3-phase distribution). European homes get 230VAC for everything unless they are lucky enough to have 380VAC.

The only major disadvantage of the split system from the consumer point of view is that portable high power consumption devices such as powerful kettles are not available due to the limitations of the wiring and receptacles. I can buy a 1500W kettle, but my European friends can get a 3kW kettle and have their Earl Grey tea ready much faster. The same gauge wire as in Europe can be run to major appliances such as stoves, range tops, electric dryers and central air conditioners, optionally with a neutral to run things like controls and small lamps.

There may be slightly more capital cost in the wiring, however the lower voltage is safer so the receptacles and cords and so on can be made a bit cheaper.

But basically there's no reason to change the voltage in either case.

The big improvement would come from going to distribution of 3-phase which would allow longer life devices and more efficient motors.

(of course industrial and commercial applications can and do often use different voltages from residences, for example in Canada 600VAC is used industrially, which explains the 346VAC ballasts used for lighting in an office I frequent- the wall switches are similar to 120VAC ones but made better).


The premise of your statement is incorrect. Industrial and commercial installations routinely use 380-415V (outside of North America) and 480-600V in North America, and that's just looking at what is called "Low Voltage" distribution.

RESIDENTIAL mains power is deliberately kept at lower values because anything higher requires different (and very expensive) design considerations in order to remain safe enough for unsophisticated users to be interacting with it. Even at 240V and 120V levels, many many people are injured by electrical accidents now. At higher voltages the rate of injury would increase, as well as the severity.

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    \$\begingroup\$ There are parts of Europe where 400/230V three-phase supplies are common, even to houses. Small appliances are run phase-to-neutral. Larger fixed appliances are run three-phase. Such appliances often have terminals that can be converted to single-phase if necessary. \$\endgroup\$
    – Simon B
    Jun 20, 2018 at 22:35
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    \$\begingroup\$ "lower voltage" isn't provided to domestic properties for safety, its economic. Single phase 230 is 3phase 400. A domestic property can request a 3phase feed but need to pay for it \$\endgroup\$
    – user16222
    Jun 21, 2018 at 13:20

By the time Nikola Tesla invented the AC distribution network, he had calculated that the optimal voltage/line frequency is 220V/60Hz with the prices of copper, steel and insulation techniques at that time.

The US adopted 60Hz, but 110V for compatibility of older Edison 110VDC machines. In Europe, Germany adopted 220V but 50Hz, to make their devices incompatible with US for warfare purposes.

This is still in use today. It's not just about using last Windows edition or change a firmware in the iPhone, it's about a huge infrastructure built over last century, no big changes are on the way.


Many appliances don't use the given voltage directly but ("traditionally", before the advent of switching power supplies) use transformers for converting to a lower voltage. Transformers for higher voltages require thinner wires with higher isolation properties. With several hundreds of volts and insulation materials from, say, about a century ago, this gets trickier with higher voltages.

Then we have motors: those run directly on household voltage. They use collectors, using carbon brushes and contacts. Higher voltage means higher burnoff.

Normal switches (like light switches) also have more sparking for larger voltages.

So while human safety is certainly one concern, being able to construct and maintain reliably and safely working electric and electromechanical appliances at normal household power levels is actually making more specific demands. After all, human safety would rather prefer voltages like 48V.


Why we don’t use such high voltage is one question. But would it even be worth considering? I argue not. Today’s low power electronics run on switching power supplies. Having supplies that can run from rectified 400-600VAC is inefficient at low power levels - mostly inefficient in terms of material spent on manufacturing. A charger brick that can safely run from 600VAC would be easily 5-10x the volume of what we got now. And the cheap ones that are not very safe at 120VAC would be only worse at 600VAC.

600VAC rectifies to almost 1kV. I have a DC voltage standard where the 1.2kV DC supply broke down and burned the PCB across track spacing of about 10mm. Now this was precipitated by local contamination, but it happens. That was from a supply of only 30mA capacity. Having 1kVDC rectified from mains at current capacity of say 10A is a scary proposition. That’s industrial equipment kind of expense at making it safe.

In short: it would NOT save anyone any money.


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