Disabling onboard video reduce power consumption?

This is a crosspost with the nvidia video forum...

Was wondering if anyone knows whether disabling the onboard video on ATI chipsets like the 690G series will reduce power consumption or not?

I know you can "disable" the onboard video in the BIOS. That's nice. But then if I add a separate video card, am I basically just powering two video cards when I only wanted one?

I'm interested in uATX sized boards to make a small system, but almost all of them come with built-in vampire video that I don't want.