At 11:58 AM 6/10/2010, mcneely4@cox.net wrote:
>David, thanks for catching and owning up to your own error ;-).

That's the engineering version of "he has to be right."  I have awful
trouble getting shrinks to understand the difference since that's
psycho-jargon as well in the sense "he has to be perceived to be right."

>   Of course, for the comparisons to be complete and properly
> related to the point in question, one would need to calculate total
> life cycle energy use, not just energy use by the unit itself.

This is of course true, and there are more highly machined parts in
an A/C than in your average heater.

>   Consider transportation energy use for the propane, and
> transmission loss for the electricity for example.

I counted that as a wash, although I strongly suspect that the
numbers favor electricity.  Once you start moving things in trucks
the costs go up pretty quick.  Average line losses in the US power
grid were about 6.5% in '07.

>   Efficiency of the power plant itself would need to be taken into account.

I allowed for 30% plant efficiency.  That's deliberately ignoring
co-generation schemes which use the turbine exhaust heat in
lower-grade applications, so I think that's at least fair.

>   It is a complicated matter.  DMc

Agreed.  But I think it merits serious thought about uncritically
accepting statements about relative eco-footprints of all sorts of
things.  People making those statements often have an ax to grind,
and I increasingly believe that there's a moral subtext involved --
until it's considered equally immoral to heat your house/car/whatever
higher than say 50F in the winter, I view with suspicion moral claims
against cooling the same house.  I also think there's a certain
amount of posturing going on.  I read with some astonishment a couple
years ago the results of a poll in which an extraordinary number --
well over half -- of Prius owners agreed with the statement that a
primary reason for buying the vehicle was to give the ^appearance* of
being "green (not suggesting that you're one of them).  I find this
distressing in many ways.

Yours,
David