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 20 times.
As for power consumption, officially GTX 1660 has the same 120W TDP as the GTX 1660 Ti. That being said, disabling one TPC on the TU116 GPU seems to make some difference, even if it is not much. That's because we saw total system power draw hit 162W, 7W less than Gigabyte's GTX 1660 Ti OC 6G and 17W less than MSI's GTX 1660 Ti Gaming X.