We measure system-wide power draw from the wall while the card is sat idling at the Windows 10 desktop for 30 minutes. A reading under load comes from running the 3DMark Fire Strike Ultra stress test for 30 minutes.
Power draw does increase for the Gaming OC 1660 SUPER, it's 27W higher than the 1660 Ti and almost 50W higher than the 1660. This does look like a worst case scenario, however, as the Palit 1660 SUPER draws about 30W less, so Gigabyte must have opted for a higher power limit.