Good old hawaii war elephant 250w, $0.1/kWh, power costs to run 'only' $0.5/ day. Still profitable.
We need to cut another 50%.
Sh0rtcoin is the best coin, hands down the best performer of the 2018 so far.
50% is too much (too short_optimistic, i.e. pessimistic) for BTC. Some altcoins, maybe.