Siggy wrote:
A while back there was a discussion about why wall wart transformers that
were not under load would draw no current. Anyone recall that thread? As I
recall there were some references to the induced currents created by
collapsing magnetic fields etc.

Anyway, I'm trying to either prove or disprove the statement that unplugging
wall warts when not actually using them to power or re-charge your device
will save electricity. My recollection is that it doesn't matter. Right or
wrong?

Iron losses are constant for all loads including none.
Copper losses are proportional to the load.

You will save the energy used by the iron losses. Whether
this is enough to make more than a few cents difference
in a year is the question.

Assume 1/4 watt loss and $.20/kw.

(1/4 / 1000) * 24 * 365 * .20) = $0.438 per year.