Measured draw (original DOL-001 / DOL-101):
The external PSU (DOL-002) is rated 39 W / 12 V 3.25 A (early) or 46 W (later). Actual draw stays well under rating.
GameCube is notably efficient—custom IBM PowerPC "Gekko" @ 485 MHz + ATI "Flipper" GPU on 180 nm process.