I've just measured it with wattmeter. Xeon E5-2697v2, 64GB ram, SSD + 2x HDD, GTX1080. Excluding monitor, that might add another 15W according to its "energy us

I've just measured it with wattmeter. Xeon E5-2697v2, 64GB ram, SSD + 2x HDD, GTX1080. Excluding monitor, that might add another 15W according to its "energy usage bar" which sits at about 25%. 110W "idle" with firefox running + few opengl programs. 160W at steam startup, then it jumps between 120W and 160W. It stabilizes at 110W in about 2 minutes. 130-230W when compiling emacs (takes about 30 seconds). 150W when loading Facebook in Firefox. Then stable at 110W again. 175W-180W running Prison Architect. Very safe to add another 220W when running GPU heavy game (thats not very relevant here, new GPUs consumes ~same or more power). I'd say my "randomly guessed" 130W amortized is pretty OK. And remember, this guess was for reference only, scale it to your needs. Of course it can get higher when having a lot of things up and running, with a lot of active tabs in firefox.