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From: ark@alice.UUCP (Andrew Koenig)
Newsgroups: net.consumers
Subject: light bulbs
Message-ID: <3362@alice.UUCP>
Date: Fri, 1-Feb-85 16:58:25 EST
Article-I.D.: alice.3362
Posted: Fri Feb  1 16:58:25 1985
Date-Received: Sat, 2-Feb-85 14:06:16 EST
Organization: Bell Labs, Murray Hill
Lines: 24

Let's see: if a 100-watt light bulb costs $1.00 and electricity
costs $0.10/kwh, then the bulb costs $0.01/hour to operate.

If the bulb lasts 750 hours, it uses $7.50 worth of electricity
over its lifetime.

Light bulbs that last longer do so by running cooler, hence more
efficiently.


Suppose for instance that you could buy a light bulb
for $1.00 that would last forever but was 25% less efficient,
so it gave as much light as a conventional 75-watt bulb.

Such a bulb would cost $0.01/hour to operate, since the
initial cost would be amortized over as long as you like.

However, one could also use a conventional 75-watt bulb
instead.  They last longer than conventional 100-watt
bulbs -- about 1000 hours, and also cost about $1.00.
Thus the cost of the bulb is $0.001/hour and the cost
of the electricity is $0.0075/hour, for a total of
$0.0085/hour, which is a 15% saving over the infinite-life
100-watt bulb.