Power consumption (was: free to good home, 19" CRT)

[Benjamin Scott]

On Sat, 16 Apr 2005, Paul Lussier wrote:
> Peter Dobratz <peter at dobratz.us> writes:
>> I have a KDS 19" CRT that ran X at 1600x1200 under Debian unstable for
>> many years.  It's still a perfectly good monitor, but it draws close
>> to 90 Watts of power
>
> If my calculations are correct, that's only .75 amps at 120 v., which
> seems rather low.

   I think state-of-the-art tubes might draw a bit less then that, but 90 watts 
is still reasonable for a tube that big.

   The real gain you get is when you switch to LCD.  A 17" LCD panel (roughly 
equivilent to the viewable area you get with a 19" tube) might draw, say. 40 
watts.  That's a 50 watt difference.  Let's say you use the display four hours 
a day.

   50 watts = 0.05 kilowats * 4 hours * 30 days = 6 kilowatt*hours/month

   6 KWH * 7 cents/KWH = 42 cents/month = $5.04 savings/year

   Compared to the cost of a few hundred bucks for a nice new panel display, 
that doesn't exactly blow me away.  Of course, there are other factors in a 
panel, including physical space savings and waste heat (for people who like it 
cool in the summer, or who live in hot climates, the savings on A/C can be 
substantial).  Even so, unless the panel was obtained "for free", I don't see 
a reasonable ROI.

   Of course, if the panel is on 24x7x365, that works out to a much larger 
savings (roughly $30/year).  But like Paul says, does it really need to be on 
all the time?

   This assumes the electric rate, of course, which varies wildly around here. 
Maybe someone has a very high electric rate.

   This also assumes immediate financial burden is the overwhelming decicion 
factor; perhaps one is very concerned about power consumption for other 
reasons.

-- 
Ben <dragonhawk at iname.com>