Question from Amir H.: I just bought a new computer and on the back is a switch labeled 120V/240V. What is this switch used for and do I need to change it? Thank you.
Rick’s answer: Hi Amir. The switch you’re asking about is used to select the proper input voltage for the computer’s power supply unit (PSU).
Here in North America the power that comes out of a standard wall outlet is roughly 120 volts AC, but in many places around the world it is twice that (approximately 240 volts AC). The red switch on the back of the PSU needs to be set to match the output voltage of the wall outlets where you happen to live.
You didn’t mention your location, but I retrieved your IP address from your email header and discovered that it was sent from New Jersey. If you live in New Jersey and you purchased the PC in the United States, you shouldn’t have to mess with the red switch at all because it should already be set to the 120V setting.
In short, if you purchase a computer in the United States, Canada or Mexico, you won’t have to change the red 120V/240V button at all regardless of which of those three countries you ultimately plan to use the computer in since they all use 120V AC. But if you take that PC to Europe or many other countries around the world, you’ll need to move the red switch to 240V.
This page contains a handy chart that lists the various countries of the world along with the voltage supplied by their standard wall outlets.
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