[ezfe]

While it's true, the US does supply 120V±5%, appliances and equipment are operable on a much wider range.

For example, my laptop charger is rated for 100-240V, which is not uncommon.

[p1mrx]

120V-5% is still greater than 110V.

Power supplies are rated for 100V because that's the voltage in Japan. Though the tolerance would probably be useful for running a really long US extension cord.

[MichaelZuo]

Technically they function fine as low as 95V for the worst case scenario, if they're well built.

[Kirby64]

Nothing to do with well built usually, just designed to work in all regions (specifically, Japan, which has 100V power for because of... reasons).

[Moru]

My old computer started burning in some internal cabling about 30 years ago. Turns out our power wasn't 230 V when the power company came and set up a machine to make a graph. Some times of the day it could be much lower and that made my ancient atari converted to a towerbox to burn the cable to the harddrive on booting.

[analog31]

That's a fairly recent development, mainly limited to switchmode power supplies.

[version_five]

Laptops and other electronics are often the same between North America and europe, just with a different plug, thus the wide tolerance. For anything with a motor or coil this probably won't work

[chociej]

100-240V 50-60Hz switching supplies are common "worldwide" or "universal" adapters, definitely not an indication of service voltage standard here.

[doikor]

The 100V low end is there due to Japan.