I have 1300w evga gold and with 3 470-s it crashes. With gpu-z i had ~63w and spikes up to ~98w
gpu-z show only power meter inside gpu proc, it is not all card power draw, only W at wall will show you truth, gpu-z show 98W for my rx 480 , but from wall i know it take at least 140W (power on load minus power on idle and divided by cards)