In art. , mm wrote in part:

Is 2 to 2.5 cents per 24 hour day not worth worrying about? 2.5 cents
is 9 dollars a year, times however many of these one has. Maybe 10? =
90 dollars a year, plus 90 dollars of wasted electricity and fuel at
the electric generating plant, plus half of year as heat that people
use AC to remove, another 90 or 180 dollars.

I think that air conditioning bit is exaggerated.

If you convert 90 dollars worth of electricity to heat, and half the
year you have to pump out the heat, that is 45 dollers worth of heat to
pump out per year.

Divide by the COP - which is (ideally) the EER divided by 3.41 (number
of BTUs in a watt-hour). COP may be somewhere around 3 or 4 in practice;
I would have to check that out better.

If COP is 3, then walwarts consuming $90 worth of electricity annually
in a home where it is air conditioning season half the year will add $15
to the electric bill.

Meanwhile, that 2.5 cents per day sounds a bit high. It appears to me
that a worse older type wallwart has idling losses around a watt or two,
based on heat output.

This is about .7 to 1.5 KWH per month. Even at Philadelphia residential
rate surcharged for use beyond some threshold during air conditioning
season, maybe 18 cents per KWH (IIRC), that is at most 27 cents per month
during air conditioning season. Without the surcharge, the per-KWH rate
including transmission fees and taxes is about 14 cents, for a maximum
around 21 cents per month.

However, I do think this adds up, especially when you have a lot of
them.

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Consider energy efficiency next time you are shopping for a fridge.
That can make a difference of a couple dollars a month.

If you have some really old fridge made in the 1970's or before that has
not died yet, find out how much electricity it is consuming, then
determine a rate of return from replacing it. There is some chance that
could exceed the long term rate of return of a good mutual fund,
especially considering that electricity costs are likely to increase
roughly with inflation in the next decade or two.

- Don Klipstein )