On 2008-04-13, RicodJour wrote:
On Apr 13, 11:17 am, Wayne Whitney wrote:
On 2008-04-13, RicodJour wrote:

With a tankless someone could take a longer shower at the same
temperature for the same amount of money, if that was their
preference.

I don't think that is actually true--the marginal efficiency is about
the same for a tank and tankless, assuming comparable combustion
technology (i.e. both 80% non-condensing). The tankless wins by
eliminating the fixed standby costs which are basically independent of
usage. So you could rephrase your statement as "with a tankless
someone could choose to spend some of their savings on a longer
shower, and still come out ahead, if it isn't too much longer."

So, you don't compute standby loss dollars in your scenario... Any
other actual dollars spent that don't count in your theoretical
calculations?

No, it's not that the standby losses don't count, it's that they don't
depend on usage. I guess I read your original statement as being one
about incremental usage costs, in which case they don't appear. But
apparently you were referring to average usage costs, where they do.

Cheers, Wayne

P.S. Analytically, what I'm saying is that a tankless will cost R * U
dollars/month, where U is the usage in gallons/month and R is a rate
in $/gallon. While the tank will cost you S + R * U, for the same
rate R, where S is the dollar cost per month of the standby losses.