Whats out there, units sold range in efficency from 55-95%, go towww.energyster.gov�and learn. If you want to save energy you must
shop by EF rating, not burner efficency, EF is how many cents on the
dollar go to heat water. Most of what is sold is 55-65EF so 45 -55 %
of your fuel is wasted. There are condensing tank of arounf 80 EF,
there are Tankless which I have of 82-95 EF. Tank water heaters are a
main waste of energy in the US. AO Smith makes the better stuff.

tankless are a bad idea for most people, they have so many trade offs
and by the time you pay for the install its a loser.