This. Hawaii needs some tweaking to be more efficient. Obviously it will never get to pascal levels in terms of power consumption but still with this weeks earnings they are still very profitable. Yes you need to flash bios on linux to downvolt.

I have a rig with two 295x2 (=4x290x), not even trying to save power with it. 1050/1250 gives 29MH ETH + 870MH DCR, 1200w at the wall.

300w is 7.2 kWh/day which makes $1.22/day with $0.17/kWh. Next week earnings could be different, you never know with cryptos...

edit: you can also save power by lowering clocks/ dpm state. Gpu-z to save your bios, hawaiireader to read what clocks are at different dpm states and then try those clocks. Easy way to save power without modding bios.