For testing power consumption, we took our test system and plugged it into a Kill-A-Watt power meter. For idle numbers, we allowed the system to idle on the desktop for 15 minutes and took the reading. For load numbers we ran three games at 1920×1080 and averaged the peak results seen on the power meter.
Power Consumption Results: The NVIDIA GeForce GTX 770 SLI setup uses roughly 20 Watts more power at idle than a single card and about 200 Watts more at load! The NVIDIA GeForce GTX 770 2GB reference card has a TDP of 230W, so this is right about where we expected to see the 2-way SLI configuration land. NVIDIA recommends at least a 600 Watt power supply with a minimum +12V current rating of 42A for one GeForce GTX 770 video card. Since each card has a 250W TDP, it is safe to assume that you should have a 850W or larger power supply for a setup like this.