How many USB devices can I plug into my desktop before I should consider getting a powered hub?

you are not affecting your CPU in any way… the amount of electricity that is available for USB devices to draw varies from computer to computer, but generally speaking, you’ll know you need a powered hub when one or more of your devices won’t function, or will function erratically.

additionally, if you have a mac, you’ll get an error message if you try to plug in too many devices at once. i’m not sure if windows or linux have similar messages.