There are no external switches to easily change to 220. And even when you open the HD20 enclosure, there are no external switches you can immediately see, nor are there any stickers in view that talk about 220. I therefore will have to unmount my power supply and then disassemble it to determine if there is a switch inside. Even so, you would have to be willing to do that work yourself, even if there is a switch inside. I myself wouldn't consider that hard, but everyone is different.