"desgnr" wrote in message
...
Would there be much difference in operating costs for a 40 gallon gas
water heater vs. a 30 gallon ?


Not really. It takes a little bit more to keep the thermal mass warm all
the time, but you have more water to draw from when needed. The real cost
is the energy needed to heat up the replacement water coming into the tank.
Tanks are better insulated today than they were years ago. My 40 gallon
tank can hold the water hot for a couple of days with no added heat if no
hot water was used is used.