m Ransley wrote:
Most of the energy is waisted up the flue to the outside, the other
losses are standby, heating un needed water, lime scale and inefficient
80% burners. Procrastinate, analayse, calculate all you want, Im getting
a 4 yr payback with my 800$ Ng Bosch pilotless tankless. And only
heating water I use.

Don't count on that payback. The Bosch heaters are very high
maintenance. Maintenance costs will eat up all your gas savings and
more. How do I know? I own one myself. It's nice when it works, but I
do not recommend them at all.