What about the P104-100 models ? Some people here have started buying them and are getting pretty impressive hash rates.
I did some research on these and they were getting them to 40+ Mh/s with 180 watt. So that would be the most efficient one. I only didn't find where to buy them, nor a price for them.
That is POOR efficiency for ETH - I see a bit over 100 watts on STANDARD 1070 models to get 31 Mhash/sec as of RIGHT NOW.
Pushing power higher doesn't help hashrate, as they are DEFINITIVELY memory limited.
On Zcash, 1070 ti cards generally can exceed 4.4 sol/watt on a SUSTAINED basis - 460 sol/sec at 104 watts - don't just look at the "best figure" as that's going to be misleading as all of the current ZCash miners do a "instant check" on power draw and sometimes catch it in a "momentary DIP" that is not representative of what the card was actually drawing for most of the several second period between readouts by the miner.
This isn't a "miner" issue, as Nvidia-SMI does the same thing.
The best figure I've seen for any 1080 ti model was a bit over 4.1 on a "sustained" basis - 620 hash at 150 watts - but I could see one managing a bit better with more work on "tweeking" done.
Those figures are using EWBF - depending on the card and the settings, you might seem more out of DSTM or Bminer (I don't do Zcash mining on Windows though except for ONE gaming machine that normally runs Nicehash).
