[svlug] Sheevaplug ?

Rick Moen rick at linuxmafia.com
Wed Oct 21 19:44:34 PDT 2009

I wrote (about the old VA Linux Systems PIII server running 24x7 on aDSL
w/static IP at my house):

> My best guess is that the _rest_ of the system's about 50 Watts.
> So, make that about 80-100 Watts system-total, at typical loading levels.
> We can of course get a better figure using the Kill-A-Watt.

So, it may or may not (I hope "may") be of interest to figure out what
that does to my residential PG&E bill.  Probably, analysis that follows
will apply similarly for most folks on this list.

Again, this is a write-up I sent, a while back, to my family (and note
that my server probably draws closer to 80-100 Watts, not 200 Watts, so
cut the closing figures in half):

 To: my family
 Subject: Understanding our electric bill

I figured it was time to understand how the electricity portion of our
PG&E bill actually works, especially since we're in the variable-rate
billing program ("SmartRate").  Good news:  As expected, we're coming
out ahead on SmartRate fees.

If that's the limit of your curiosity, you can ignore the rest of this
mail, which details how our electric billing works.  (Gas billing isn't

Going by the Aug 13 - Sep 13 bill, we use about 690 kWh per month, 22
kWh per day.  It seems fair to consider that typical, because I doubt
our usage varies much, certainly not seasonally.

The bill says rate schedule "E1 XB Residential Service" applies to us.
E1 is standard residential.  X is a non-coastal region, and B means
house heating isn't provided by electricity.  This PUC classification
determines the amount of electricity we're allowed to buy at the
discounted "baseline" rate, and how high that rate is.  E1's electrical
baseline/rate is _not_ seasonal.  Some other plans get different
baseline quantities and rates between summer (May-October) and winter
(Nov.-April) months, but ours has a constant rate.  (Our gas baseline is
seasonal, however.)

Rate tiers are graduated, as with income tax brackets:

Tier 1 Baseline:              First 387.2 kWh   costs $0.11531 per kWh
Tier 2 101-130% of baseline:  Next 116.16 kWh   costs $0.13109 per kWh
Tier 3 131-200% of baseline:  Next 185.4094 kWh costs $0.25974 per kWh
Tier 4 201-300% of baseline:  Next 271.04 kWh   costs $0.37866 per kWh
Tier 5 300%+    of baseline:  Additional usage  costs $0.44098 per kWh

Our monthly usage tends to hit Tier 3, which means adding to or reducing
from our usage costs or saves us $0.25974 for each kWh.

[snip details of how SmartRate affects all this.]

This permits guesstimating the monthly electricity cost of running a
home server 24x7.

If you assume (for the sake of discussion) 200 Watts of power draw for a        
server, running 24x7:

200 Watts / 1000 watts per kilowatt = 0.2 kW                                    

0.2 kW * 24 hours/day * 31 days/month = 148 kWh per month

148 kWh per month * $0.25974 extra cost / kWh = $38.65 per month extra

...or about $40.

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