Now, I’m not sold on this whole green­house thing just yet (The Great Global Warm­ing Swin­dle had at least as much sway over my opin­ion as that Pow­er­point pre­sen­ta­tion to which it was, per­haps, a coun­ter­point), but as a mat­ter of mere con­sump­tion (and intel­lec­tual curios­ity) I was keen to learn just how much power one of my com­put­ers, in par­tic­u­lar, was using annually.

This one sits in a cup­board, answers to the name of ‘whis­per’, reaches obscene tem­per­a­tures in sum­mer (yet does not crash), and, at its heart, fea­tures a low-power-consumption proces­sor and moth­er­board by VIA. It also has two hard dri­ves and a sin­gle 512MB (8-chip double-sided (16 total)) DDR-400 DIMM.

And that is all.

Most of the time, it’s rel­a­tively untaxed… it acts as file stor­age, a web server for mis­cel­la­neous stuff I want to share quickly, and a devel­op­ment box for more adven­tur­ous things. At one stage it was host­ing stream­ing media (and, very very briefly, a Counter-Strike server… it is hor­ri­bly under-specc’d for such duties). It’s also use­ful for SSH’ing into and bypass­ing prox­ies when you really need to get to some­thing (entirely legit­i­mate, mind), but increas­ingly less so as a cer­tain work­place of mine blocked SSH out access when we moved floors. No mat­ter — I’ve iden­ti­fied a HTTPS-SSH solu­tion to that par­tic­u­lar prob­lem, but haven’t been moti­vated to imple­ment it just yet!

So, here’s the run-down:

			Load	Idle
VIA EPIA PD10000	23W	15W
Generic 512MB		2W	1.5W
ST380011A		12W	8W
ST380011A		12W	8W
			49W	32.5W

Most of those have been rounded a lit­tle bit, but… let’s just say it only uses 49W at the most.

Then, there’s the 65%-efficiency-at-full-load (230W) power sup­ply to con­sider. We’re no-where near full load, but let’s just say it’s con­sis­tently effi­cient (or, in-efficient) regard­less of load. In prac­tice, it’d prob­a­bly be slightly bet­ter for lower loads due to reduced heat production.

So, our 49W sud­denly becomes (49x1.35) 66.15W

That’s 579.47kWh/year, which (appar­ently) equates to about 400KG of emis­sions. This, friends, is absolute worst-case sce­nario. More real­is­ti­cally, the sys­tem will be idle most of the time, using 384.3kWh/year, and pump­ing out around 260KG of carbon.

I’d be inter­ested to see how this would com­pare to a typ­i­cal lap­top computer.

For this par­tic­u­lar com­puter, there’s only a lit­tle that can be done to improve effi­ciency. The obvi­ous tar­get is the two hard dri­ves, which, com­bined, draw nearly as much power as the rest of the sys­tem! Con­sid­er­ing there’s not a dra­matic amount of stor­age presently in use, I could almost jus­tify replac­ing these with a solid-state device (in the form of an IDE-card reader bridge, because real SSD dri­ves remain pro­hib­i­tively expen­sive and dif­fi­cult to obtain in this coun­try) if the need were really there.

And what would cre­ate such a need? Well, part of the rea­son I wanted to find out was to see how many hours this thing could live off a fairly cheap UPS for. Turns out it’s prob­a­bly got at least an hour’s worth of life in it, which is mod­er­ately incred­i­ble com­pared to the typ­i­cal ten-minute-or-it’s-fsck-time expected para­chute expectancy!

The only prob­lem in adding a UPS is that they’re not the world’s most energy effi­cient devices them­selves, with an APC 500VA model chew­ing 24BTU (82.02W, since we’ve been work­ing in that thus far) per hour when “online”. BTU is a mea­sure of ther­mal energy dis­si­pa­tion, by the way, so prob­a­bly it’s also less-than-ideal for stick­ing in a cup­board in which the next-largest heat source is prob­a­bly the power sup­ply at a mea­gre 17.15W (assum­ing its inef­fi­ciency is purely ther­mal, which, of course, it won’t be — other non-thermal radi­a­tion must account for at least some of its loss).

So, there we go. A fairly use­less exer­cise that will become mar­gin­ally less use­less if ever there are rolling brownouts in Syd­ney and I need some­thing to be able to weather the power storm. The other great thing about UPS is they pro­vide fairly decent power con­di­tion­ing, too. Given you can pay about $50 for a decent 6-way surge pro­tected board, or only $140 for a 500VA (300W) APC UPS these days, it’s really not that bad a deal afterall.

Sources:

VIA EPIA-PD10000 power usage: http://www.via.com.tw/download/mainboards/3/4/OG_EPIA-PD_111804.pdf
Generic 512MB DDR-400 mem­ory power usage:
My mem­ory, from prior read­ing and specs of higher-quality mem­ory that actu­ally pub­lish such data.
Sea­gate ST380011A power usage:
http://www.seagate.com/support/disc/manuals/ata/cuda7200pm.pdf

SFX-230M2 switch­ing power sup­ply (used by a lot of big OEMs like Dell and HP, it turns out) spec­i­fi­ca­tions:
http://www.sirtec.com.tw/photot2/10205/210205R11.pdf