Non-gaming power consumption has been improved a little bit over other Turing cards, but the differences are too small to really matter. Previous-generation Pascal cards are slightly more efficient in those states, but, again, with negligible effects for real life.
Gaming power consumption of the GTX 1660 is highly impressive. With only 109 W during gaming, the EVGA GTX 1660 is super efficient and uses less power than the GeForce GTX 1060, while delivering more performance at the same time. Compared to the Radeon RX 590, which is built on a 12 nanometer production process, too, the GTX 1660 uses just half (!) the power and is faster.