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Ralph Mowery

In article ,
says...

I have an old PC that recently lost its PS. An identical one was hard
to find, but I didn't know the PC's power requirements, so I couldn't
use a generic PS. I should say that I thought I couldn't use a generic one.

I measured the PC's power use so next time I'll be ready. It was quite
surprising - the PS is "400W", but the PC only uses 54W. And there's
40A of 5V available, but only 5A are used. Etc.

The biggest surprise was the PS's efficiency, or lack thereof. A
Kill-a-watt on the input showed 200w being used, and 54w output. 25%
more or less. I thought that a SMPS would be way more efficient than that.

Bob

I don't have a Kill-O-Watt but do have a meter similar to it. That one
reads out Volts, Amps,and Watts. I have noticed that if I hookit to a
resistive load like a heat gun the volts and amps are very close to the
watts. If I hook it to a reactive load there is a big difference in the
Watts vers the volts times amps. That I understand.

I have not paid any attention to a switching supply that way. Is it
possiable the the watts and the V times I are not the same for your
meter ?