Currently, my rig has 750W PSU. With 3 cards running 100%, power draw at the wall is 590W. The cards I'm using are RX470 4GB, and in GPU-Z the power usage for each card shows as 95-105W while I'm mining.
I'm wondering if I'm able to add another GPU, increasing wattage by ~105W, making my rig run at ~695-700W on a 750W PSU? Is this trying to put too much load on the PSU? I know basic mathematics say it's ok, but I don't know enough about PSUs to know if it is reasonable of me to expect my PSU to be under 700W load 24/7. Thanks for the help!
no.
do you want the long explanation?
here goes the 95-105 is a software number not a real number
105+105+105 = 315 lets say you are a 90% psu 315 /90% = 350 at the wall
so you said you pull 590 at the wall that is 240 watts for your setup
if you have an insanely jacked cpu it is 135 watts = and you are crazy to use it.
most likely your 3 cards are pulling 450 at the wall or even 480
a fourth card would then bring you to
590 + 150 = 740 or
590 + 160 = 750
now lets say you have a 90% psu it means you are sending 750 x 90% = 675 into the unit
675 out of 750 is a true 90% draw on your psu which is never recommended for atx gear.
if you want to run 4 cards you will need a better psu or clock and volt the four cards lower then you are doing.
Of blow me off run the four the way you say and see if I am wrong or right.
your gear not mine.