Enegy Consumption: Correctly Scaled Power Supply

22 06 2010

One of my main goals of the NAS project was to make it as low power as possible while still functioning.  For me that meant a system that was largely in standby mode and that when running consumed as little power as possible. My first step was the use of low power hardware (motherboard, disk drive, etc) and then my latest step just this week was to move it to a case with a much more efficient power supply.  In this brief post I want to focus on the power supply overhead I saw in my project.

I had an opportunity to look at the impact on badly matched power supplys in my stepwise process of building my home server.  I first built it in a standard ATX case with a standard ATX power supply (350 W I think?) but I used low power Atom board and hard drives (1 2.5″ PATA and 1 3.5″ Green Series WD)  running Windows Home Server 1.0.  After using it in that configuration I moved it into a Chenbro ES34069 with a 120 W power supply that was more efficient at lower loads.  I took advantage of that opportunity and took some notes about energy consumption.  The following are the measurements in 4 different power states, the energy consumption of the 2 configurations, and the percent change between the two:

ATX Chenbro % Change
Off 3 W 2.5 W -16.5%
Standby 3 W 2.5 W -16.5%
Running – Load 42 W 32 W -23.8%
Running – Idle 39.5 W 28 W -29.1%

In all states the power consumption decreased.  In the off and standby states the drop is really negligible but in the load and idle states the reduction is fairly impressive considering the only thing that changed was the efficiency of the power supply in the setup.  After looking at the numbers I wondered how they compared to if I was to run a desktop in the similar setup.  So I measured the usage of my 1 year old Dell Vostro 220 system to throw into the mix.  I did the same measurements but unlike the other two setups the consumption was highly variable.  To account for that I decided to use the consumption specifications that dell provides because they were right in the range I was measuring.  Here is the beautiful graph I made…

Graphical Representation of Measured Energy Consumption

Graphical Representation of Measured Energy Consumption

Eventually I’d like to take this data and expand it to energy usage in 1 year but for now here are the immediate measurements and comparisons.



One response

27 01 2011
Hans Göttinger

Thanx for posting numbers on Chenbro PSU draw, would have been nice to compare that to an Gold PSU or and PICO PSU. Iam also trying to build a low energy NAS, biggest problem by far is to get an low power PSU with good idle % efficency. I have not found any figures on Chenbro PSU.

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