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From: mario@cs.man.ac.uk (Mario Wolczko)
Newsgroups: comp.misc
Subject: Re: Leaving computer equip. on (was: Monitor reliabilty)
Message-ID: <1712@m1.cs.man.ac.uk>
Date: 17 Sep 90 16:09:19 GMT
References: <1081@beguine.UUCP>
Sender: news@cs.man.ac.uk
Reply-To: mario@cs.man.ac.uk (Mario Wolczko)
Organization: University of Manchester
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In article <1081@beguine.UUCP>, Jeff.Miller@samba.acs.unc.edu (BBS
Account) writes:
> Assuming each draws 50 watts (resonable for 19" monitors) and that you pay
> about as much for your power as I pay for min (not so reasonable: as part
> of an institution you may pay less, but not less than half I am sure), you
> paid US $13,000 (about 7,200 pounds, I think) for power for these monitors
> for that time period. If you kept them turned off 12 hours a day, you would
> have saved $6,500, enough to pay to have all of them fixed and perhaps
> quite a bit more. (Assuming you had them fixed by an independent :-)
4years x 365d x 24h x 0.050kW x 65 / (12hrs/24hrs duty cycle) = 56940 kW h
At approx 5p per kW h (domestic rate, don't know what the commercial
rate is), this is 2847 pounds, somewhat less than you calculate, but
of the same order.  

That budgets 258.81 pounds (approx $500) per repair, _assuming the
reliability is the same_.  If the reliability halves (which I think is
being _extremely_ optimistic, as we are talking about _at least_ 1000
power cycles per monitor, at least 65000 in all, and probably much
more as many are shared), I think the repair costs are likely to be
more.

> To say nothing of the environmental impact.
>  
> I think everyone in the computer feild and especially the Unix community
> should give serious thought to power consumption. It is no joke. If there
> are 1 million machines out there, and each draws on average 200 watts, that
> is 200 megawatts. To say nothing of the air conditioning. Leaving them off
> for 12 hours a day would spare a 100 megwatt plant. Not much, unless they
> want to build it in _your_ backyard. 
>  
> Just think about $1.00 per watt per year to figure how much a given piece
> is costing you. 

This is an incredibly specious argument.  How much energy do you think
it costs to make the parts for a monitor?  What about the cost in raw
materials?  What about the petrol used by the delivery of the parts
(most of which come half way round the world), and the visit of the
maintenance engineer?  And air conditioning..in the UK?  Tee hee...

And why are UNIX users singled out?  I've heard the expression "power
users", but I thought that meant something different :-).  

Also, most countries have surplus power at night, so I don't think you
can argue that switching machines off at night would save on stations.
Anyhow, 100MW is a small fraction (<10%) of _one station_.   

If you're going to argue a case, _present real facts_ (such as the
difference in MTBF for monitors left on vs those power cycled every
day).  Otherwise, we gain nothing.

Incidentally, the power consumption of a 3/50 drops from 140W to 125W
when screenblank becomes active: I just measured it.  Switching off
the monitor entirely saves 70W.

Mario Wolczko

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