PSU requirements?

I just noticed that my PSU is maybe a little weak ;-) I have a 700W, and when I run the benchmark on both 1070s the PC switches off ;-)

I thought I might be within acceptable range - 2x165W (GPU) + 100W (CPU+Mobo) still roundabout 60%

Any rule of thumb? 500W per GPU?
This should be based on actual power-draw numbers, which vary by hardware (and GPU).

Recommendation: get a Kill-A-Watt, measure actual draw from the wall without the GPU being at load, and then look up the specs for the GPU's expected max draw.