Current GPU with Best Power Efficiency

I am considering various GPUs for my ZEC rig. Given that RX480 and RX470 are not getting very high hashrates, which are the GPUs that I should consider for power efficiency? Electricity is relatively expensive where I am based.

GTX1080 Ti with more than 4 Sols/W at 150W TDP limit (~620 sol/s).

This site should help

whattomine.com

Looks the RX470 has the best balance in terms of power efficiency and startup costs unless I want to go Nvidia cards

GTX 1070 is wonderful.