very promising project, +rep! 

some old MSI Z77A-G43, Asus PRIME Z270-P (plus 2 biostar mATX motherboards with 2-3 pci-e on each), 2x ASUS STRIX 1080 A8G, 2x Gigabyte Extreme Gaming GTX 1080, 1x MSI GTX 1080 TI SEA HAWK X, 4x Gigabyte GTX 1080 Ti Aorus, 6 x ASUS STRIX GTX 1080 TI O11G

PSUS: Corsair AX860i, RM750x, 3 x RM 850i, Gigabyt B700H(80+ bronze isn't good)


CPU: Celeron G530(in old biostar baseboards), Celeron G3930 (in asus prime)

The cheapest HDDs(WD Caviar Blue 250 GB) and RAM

0.065$ per kWh, 3.500 kWh in total (counted with watt-meter)(11x1080Ti, 4x1080, 1x960), around 150-190$ monthly in total with other house supplies, Ukraine

got it working in some different way, ty

Got 4x1080, 3 on risers and 1 in pci-e x16 slot. If i run just 3(2 on risers and 1 in pcie) then it's working fine, but if i try to run 4 gpus at the same time, device manager says:
"This device cannot find enough free resources that it can use. (Code 12)

If you want to use this device, you will need to disable one of the other devices on this system."
for 3 gpus that are plugged into risers.

- i7 7700k, 32GB, SSD,

- MSI z270 Krait Gaming motherboard

- 2xAsus Strix 1080 A8G, 2x Gigabyte 1080 WindForce 3X Xtreme Gaming

- 3x risers 006.

- win 10-64bit

-PSUs: Corsair AX860i[i'm getting the same error when i try to run 4 gpus just on this psu] , Corsair RM750x