mike fired this volley in news:js6ao9$2pp$1@dont-
email.me:

For dilution I don't think it makes any difference. If you want a
gallon of 100F water, the temp of the hot and cold water mixed together
is irrelevant. If you mix it to 100F, you used the same number of
BTU's.

Nope, Mike. The theory is right, but the upwind losses are higher, the
higher the water temperature.

Say, for sake of arguement, that you had water at exactly 100F in the
heater all the time, and no losses in the _lines_ between the heater and
the faucet. And, lets say for arguement that the room air temperature
where the heater lives is 100F, also. And let's say the cold water is
50F.

Then you'd mix 100% hot, 0% cold to get your 100F water, and there would
be no radiation losses from the tank into the room, since the temps
inside and outside were the same.

Now, raise the tank temperature to 150F. You have to add 50% hot and 50%
cold to get to 100F. So, same number of BTUs, yes, but something else:

Now the tank is radiating heat out into the room. There are losses
occurring now that weren't before.

It's NOT the same total number of BTUs. That only occurs in
theoretically perfectly-insulated systems.

Wally doesn't have one of those.

LLoyd