In an IDLE state, a PC (motherboard (Z270) / processor / memory / SSD) consumes roughly 45 Watts. Once we add a GeForce GTX 1080 we see an increase of roughly 8~10 Watts. This number depends and will vary per motherboard (added ICs / controllers / wifi / bluetooth) and PSU (efficiency). Keep in mind that we measure the ENTIRE PC, not just the processor's power consumption. Your average PC can differ from our numbers if you add optical drives, HDDs, soundcards etc.
As always I want to make it very clear that power consumption measurements will differ per PC and setup. Your attached components use power but your motherboard can also have additional ICs installed like an audio controller, 3rd party chips, network controllers, extra SATA controllers, extra USB controllers, and so on. These parts all consume power, so these results are a subjective indication. Next to that, we stress all CPU cores 100% and thus show peak power consumption. Unless you transcode video with the right software your average power consumption will be much lower.
Overall stress/load temperatures are very nice with temps at the ~50 C marker. These, of course, are default results and not tweaked. The processor idles at roughly 30 Degrees C. We used a fairly dated but good Corsair H110 here for cooling. Overall we are very content with the temperature results here.