I believe the problem is not malware infecting your computer through the the power cable, but existing malware leaking information through the power cable.
This could be avoided if running the computer off batteries, which are only charged from main when they are disconnected from the computer.
so this is 100% true? Can anyone else verify this?
Also you can never let a airgap computer touch the network. I have no idea why that article says connect to the network as little as possible? You're supposed to never connect. Anything you move over to the airgap computer should be through usb stick and then the usb stick essentially smelted.