The S5 does not use 750W as such, it is good to have a PSU which can provide more than what the S5 needs, but you should count on around 590 - 600 watts if you run it on default (350).

This Difficulty
Coins   Dollars
per Day   0.01102199 BTC   $2.87
per Week   0.07715392 BTC   $20.08
per Month   0.33548176 BTC   $87.29
this diff (est)   0.06088698 BTC   $15.84

Minus electricity.