GTX 180 ti card draw about 260 watts each if you set them up right. The biggest issue with the GTX 1080 is needing both an 8 AND a 6 pin connector. That means a 1300 Watt EVGA PSU can only run 3 cards unless you use splitter/adapters. I like to run my PSU’s in the sweet spot for efficiency (in the end, its all about Hash/watt), so I always over buy on the PSU. For a 7 GTX 1080 GPU rig I use one 1600 watt and one 1300 watt. 8 GPU’s would be nice (with two 1600 Watt), and I have that working, but its so close to 20 amps that it can trip the main breaker, so not ideal.