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 |
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