What happens if I connect a power supply rated for 120V to a 240V outlet (or vice versa)?

Basically, if you're dealing with a universal PSU (110-240V), it should handle either voltage fine. But if it’s strictly 120V and you connect it to 240V, you’re in for a loud surprise. Conversely, if you connect a 240V PSU to a lower voltage outlet, it'll just underperform.

In short, connecting a PSU rated for 120V to a 240V outlet could lead to explosions or electrical fires. But a 240V PSU plugged into a 120V outlet would just sit there doing nothing. Always check your PSU's specs before plugging it in!

Most modern PSUs can handle a range of voltages from 100-240V, so they’ll automatically adjust. However, older or specialty PSUs might not work this way. If you plug a 120V PSU into 240V, it could get fried; the opposite (240V into a 120V PSU) would usually just mean it wouldn't work at all.

Connecting a 120V-only power supply to a 240V outlet is a recipe for disaster. It'll likely blow up or at least fry itself. On the flip side, using a 240V PSU on a 120V outlet typically just won't power up, but it’s a much safer scenario than the other way around.

Just to clarify, older PSUs with a manual switch can also blow up if they're set to 110V and plugged into 240V. I’ve had a bad experience where a PSU went up in smoke and tripped the breakers when messing with second-hand PCs. New PSUs are generally much more flexible.