Embodiments of the present disclosure include methods, systems and program products for controlling a water bath heater for a fuel gas. Methods according to the present disclosure can include: calculating at least one calculable condition of the fuel gas based on a set of conditions of the fuel gas entering the water bath heater and a type of control valve located downstream of the water bath heater; calculating a target temperature differential for the fuel gas based a set of conditions of the fuel gas entering the water bath heater and the at least one calculable condition; and adjusting an operating parameter of the water bath heater to adjust a temperature of the fuel gas leaving the water bath heater by the target temperature differential.