How much gas to run a 300000 BTU pool heater?

To determine how much gas a 300,000 BTU pool heater uses, you need to know its efficiency and the type of gas being used. Generally, natural gas provides about 1,000 BTUs per cubic foot. Therefore, a 300,000 BTU heater would use approximately 300 cubic feet of natural gas per hour if running at full capacity. If using propane, which has about 2,500 BTUs per gallon, it would consume around 120 gallons per hour at full capacity.