Yes, I don't include electricity but problem is price of a miner & shipping is too high so I can't pay for a USED miner that have ROI 4-5 months.. What if it's broken/lower hashes etc..
About free electricity:
1 S9 - 1.35kW
30 S9 - 40.5kW
960 kWh = 40kW
If you underclock them with
Braiins OS you can even add more of them. By raising efficiency you can easily lower that consumption to under 820w each (@10T)... You could put 48 S9s, maybe some more if a few have damaged boards.
480THs vs 390THs using the same 40kW...
Make sure you check more sellers, i have seen S9s at $150 each...
PLUS, under-clocking tends to make them run cooler and last longer.