DesignGuy wrote:
I'm getting ready to replace my Rheem 75 gallon gas water heater with a
Kenmore Power Miser of the same size.

However I noticed that the Rheem has a rating of 75500 input BTUH, and the
Kenmore has rating of 55000. I'm not clear if a loer or higher number is
better, as some explanations I've read seem to indicate that the Rheem would
use more BTU's to heat the water than the Kenmore (thereby making the
Kenmore more efficient).

Is my reasoning correct or is the reverse actually true?
....

No and no...that rating is related to the "first hour rating" and
correlates to how fast it will heat cold water initially. The higher
the input, the faster the water will get hot (and reheat when
recharged).

The overall energy efficiency is the energy factor (EF) and comprises
recovery efficiency and standby and cycling losses.

See (watch wrap)
http://www.eere.energy.gov/consumer/.../mytopic=12980

for an overview. There's a rating on each unit that compares operaing
costs that correlates (roughly) to efficiency but that's not the only
criterion in making a selection.

for