Quick PSU consumption question

[kossel]

Hello

If I have a 650W PSU, but my current setup is quite low end so maybe max load is 400W, how much will be the real consumption on my electricity bill for the CPU? 650W or 400 W ?

 

[Bearmann]

400W (I presume you meant PSU, not CPU)

 

[Yuriman]

400w is a pretty high load. The system in my signature rarely draws more than 150w.

Power supplies are more efficient when they're more fully utlized. If you have a 650w PSU powering a system that draws 40w at idle and 200w under load, due to lower efficiency from running the power supply, you might see 80w idle and 250w loaded at the wall.

 

[Blain]

It seems efficiencies peak at around 50-60% loads, from what I've gathered over the years.
The extra capacity also provides a power buffer for component degradation over time.