Depends on the BTU's of the heater. There are 93,000 BTU per gallon so you would take your BTU and divide by that number. 93,000 BTU per gallon / 30,000 your heaters BTU = just over 3 gallons per hour.
1400
130000 btu
It takes 8.33 BTU to raise the temperature of water 1 degree F.
114,000 BTU/gallon
It takes 8.33 BTU to raise the temperature of water 1 degree F.
140,000 btu/gallon, nominal
400 k BTU - But it depends on the gas line size feeding the heater; how long that run is etc. The larger heater will heat the water quicker thus cost for heating will be less ( than if you used a 250K BTU)
71,100 BTU per gallon of LNG.
About 115K BTU per gallon.
Ethane has 65,869 Btu per gallon.
114100 Btu