i have 3/4 inch piping about 40 feet from meter. also on gas are furnace and dryer. neither of which are used that often. Currently i have a 50 gallon tank water heater but want to go to tankless because it does not give me enough hot water for my japanese soaking tub.
aslo the tankless hot water has to be on a eprate breaker cause it is a 220 and has to be install by a pro plumber
As long as you pay the bill you will have enough gas.