From 8.0 to 9.0
6*RX 470 power consumption raised from 800W to 1000W from the wall.
Odd, mine went from ~860 to ~860.
What did you modify in the card's bios/settings? Do you have ref. cards or aftermarket (such as Nitro+, etc.)?
I measure ~900W on the wall for 6 pcs of Sapphire ref. RX470 4GB.