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efficiency enermax vs Qtec power supply

S

sonics

Junior Member
Something is puzzling me.

I have a system with a A64 3000+ venice, Asus AV8 board, a nvidia 6800LE, dvd drive and a seagate 500GB.

Running on a cheap QTEC power supply of 350W it's power usage was 78W idling in windows XP.

So next I tried my Enermax EG 365AX-VE (350W) from my other PC to find out if the Enermax is more efficient.

To my suprise the power usage was 88W. 10 Watt more :s

Any idea why an expensive enermax uses 10 Watt more than a cheap Qtec?

The Enermax does seem to get less hot than the Qtec.
 
One of them probably puts out more Amp's on the 12V rails than the other. Maybe even one has PFC and the other doesn't. It could also just be the different designs and components used to achieve that rated power.
 
Higher price doesn't always mean its better. There can be any number of reasons whay the Q seams to be more efficient then the Enermax. For one how are your measuring the power usage? If its threw any software then you can not trust those numbers. Not to mention that your power usage can very while the system is idle. Now if you where useing a set load source and a power monitor like a Kill A Watt so that you knew the actual power usage vs the power being pulled from the wall. Then you would be able to calculate the actual efficiency of each unit at that size of a power draw.
 
I'm using a Watt meter in the wall socket where the power supply plug has been put in.
I don't know the actual efficiency but I do know the actual usage.

in a wiki about PFC I read this "PFC is a required feature for power supplies shipped to Europe."
So I guess both my power supplies have it then since i live in the netherlands. But i never took any attention about it.

The enermax indeed can supply more AMPS on the 12V line, but since my PC doens't need those extra power it shouldn't matter right?
 
Well a PSU is at its best efficiency when under a mid level load. Efficiency rides a bit of a bell curve with the load. So if the units have about the same efficiency you could be getting less efficiency out of the one with the lower load on it. Or it could be going the other way araound. Its all a matter of what side of the mid range load line your system is on with each unit. Now a 10W difference in the power comming from the wall isn't all that much. its only about a 2% difference between the 2 if even that much. but not knowing the actual load the system is under makes it hard to calculate the actuall efficiency of each unit.
 
Did you measure for a sustained period of time? Like every 10 seconds, for 2 minutes, while idling in Windows, and then calculate the average? Did you do one PSU first, then the other in the exact same condition? Perhaps when you switched PSU's, and booted into Windows again, something a little bit CPU intensive was running, skewing the measurement, whose to say.
 
Regardless the difference in efficiency is about 2% which is negligible. You could probably find the same variation testing 2 of the same model PSU. 10W isn't all that much. Even if that 10W was all from the 12V rail thats only .83A. Basicly the amount one or 2 fans would be pulling. But its true that windows at idle could still be drawing a different amount of power each time the system is rebooted. Without haveing a consistant and known load you can't be sure how big of a difference there is between the units.
 
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