compared to the s7 heat output the output from the s5 is like a warm summer breeze.
And that's why I dont have antminer s7s. Sure, my fan mod sucks and the s5s I have run hot, but I can't imagine how hot s7s run. How hot is the back of it? I hear its REEEALY hot 
Of course, if it isnt I may consider buying one and adding to my rig- Mining is only a hobby for me.