Electricity Usage (was Wireless Cards)

Shane Hathaway shane at hathawaymix.org
Sun Nov 6 20:40:50 MST 2005


Charles Curley wrote:
> On Sun, Nov 06, 2005 at 07:10:36AM -0700, Hans Fugal wrote:
> 
>>On Sat,  5 Nov 2005 at 22:54 -0700, Andrew Jorgensen wrote:
>>
>>>On 11/5/05, Scott Paul Robertson <spr at mahonri5.net> wrote:
>>>
>>>>More versatile? In what way?
>>>
>>>I won't weigh in on the versatility argument, but I would like to
>>>point out that a little AP doesn't have a huge noisy fan to keep it
>>>cool, nor does it cost $10/month in electricity to run.  That means I
>>>can leave it running 24/7 without feeling guilty.
>>
>>Do you have hard evidence of that figure or is it pulled out of a
>>hat? I ask because I did some reading and thinking and came up with a
>>figure more like $10/year (or maybe it was even less) for a PC (and
>>another $10/year for a power-saving monitor)
> 
> 
> Well, let's see. My desktop PC has a 500 watt power supply, which is
> overkill, but gives you a worst case number. My Linksys WAP54G has an
> 11 watt wall power supply. Again, that's probably worst case. Now get
> your electricity bill out & crunch some numbers.

My Kill-A-Watt tells me that my little server doesn't pull in more than 
60W even if I work it hard (yet it has a 250W power supply.)  The power 
company charges me about $0.08 per kWH.  So, worst case:

60W = 0.06 kW

(0.06 kW) * (24 * 365.24 H) * ($0.08 / kWH) = $42.08

So it costs me more than $10/year but less than $10/month.

Some other figures I've gathered: My desktop machine, an AMD64 3200 with 
a SATA drive and a low-end NVidia card, draws 75W most of the time and 
120W when it's computing a lot.  It has a 480W PSU only because I don't 
want to worry about meeting the current requirements for each power 
rail.  The "ondemand" frequency scaling accounts for a savings of about 
8W (it reduces 83W to 75W.)  My 19" LCD monitor draws 30W; it replaced a 
15" CRT that drew over 100W.  My laser printer consumes 10W when it's 
idle and 700W when it's heating up.

Of course, the computer isn't usually the best place to look for power 
savings.  An electric range can draw 12 kW all by itself.  Here's a nice 
chart:

http://www.city.ames.ia.us/ElectricWeb/energyguy/appliances.htm

Shane



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