SPCR

... or is just capable of using more?

Asuming you have two identical computers with different PSUs, will one 'waste' more power than the other?

Obviously this depends on the quality and goals of a particular power supply, but in general ...?

Hello,

It all depends on the efficiency of the PSU at the power level you are using it at. Many PSU's are often at their highest efficiency at 30-80% of their rated power, so if one of the two theoretical units is more efficient at say 125watts, then yes it would use a little less power . If they are very close to the same efficiency at 125watts, then they both will use nearly the same amount of power.

You cannot know by their maximum power ratings which one will be more efficient at the power level you will use it at. This is why the SPCR reviews of PSU's measure the efficiency at a number of power levels.

most "SPCR" systems probably draw around 200w at load, and around 100w at idle. obviously this varies a bit, but considering people here are going for quiet systems, you dont see overclockers and SLI setups often that would push that number much above those rough estimates.

my current rig idles around 50-60w, and load is around 100-110watts. but i run mobile parts in my systems.

So your effeciency is going to vary depending on the current load on the PSU. It all depends on the effeciency of the PSU at the current load level, it has nothing to do with the maximum sustainable power output. All that number means is that is the highest continuous power level your psu can work at.