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From: brian@sdcc3.UUCP (Brian Kantor)
Newsgroups: net.consumers,net.analog
Subject: Re: power/energy meters
Message-ID: <2769@sdcc3.UUCP>
Date: Wed, 27-Mar-85 13:18:04 EST
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Posted: Wed Mar 27 13:18:04 1985
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Organization: UCSD wombat breeding society
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Xref: watmath net.consumers:2067 net.analog:240

To measure the cost of running an appliance, you need the integral of
energy used over a period of time.  Since the power company probably
bills you for kilowatt-hours, its reasonable to calculate it that way.

The gumball machine on the side of your house does that, but its
probably set up for 230V service, which is likely what you have.
(You know, three wires, usually a black and a red or blue hot wire, and
a white neutral.  You may also see a green or bare ground wire.)

Anyway, the outlets in your house are (except for the electric dryer,
oven, stove, or maybe a big air conditioner) single phase - i.e., they
have only got two wires (plus possibly a round pin - the safety ground).

Construction sheds, outhouses, street lights, and cable tv amplifier boxes
frequently have small single-phase power meters on them.

So here's the deal:  you can probably buy an old two-wire single-phase meter 
from the power company.  Mount it in a nice box (varnished maple is nice),
mount a receptacle on the back, add a power cord, and voila! you have a
meter you can use to figure out how much it costs per appliance.  You
can't reset it to zero, but just note down the start and end readings
for each appliance over a period of several days (a week is good for
getting a real average).  That's the number of kilowatt hours used.
Just multiply it by your power company's usurious rates and you'll know
how broke you are going to be.

Several friends and I got together to build one of these; the surplus
meter cost about $35 as I recall.  I now know that heating my waterbed 
costs about $15 a month, my refrigerator about $20 a month, my
computer about $10, my furnace $4 (blowers, you know), and the TV set
about $8.  I can't measure the stove, oven, nor electric dryer because 
the meter won't handle three-wire 230V circuits.  I haven't measured the 
electric-belly-button-lint-remover either (yet).  

(Welcome to San Diego, home of the second highest electric rates
in North America.)

	Brian Kantor	UC San Diego

	decvax\ 	brian@ucsd.arpa
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``You unlock this door with the key of inebriation...''