Monero mining gives me a much lower watt consumption, 6 580s at the wall for me was pull 1000w for ether and 6 700w for monero.
If 6x580's is pulling 1000w@the wall for ether, you're doing something wrong.
It should be way below 800w, i've seen as low as 700 with 8xx mv settings.
its all about proper overclocking / undervolting the GPU/Mem , Creating a custom bios for those cards , custom bios i mean modding the bios , not just changing the mem straps
yes you can go low with energy usage , but then you are going to miss a few MH/s on ETH mining
low energy rom - less MH/s - less power usage
power rom - more MH/s (can be additional 2-4MH/s / card ) - more power draw
bios mods need to be optimized for coin you are going to mine ... If the mod is optimized for ETH , that not going to give you the best hash rate on XMR or Zcash
If the mod is optimized for XMR , that mod is not going to give you the best hash rate on ETH or Zcash ...
Choice is always yours