Abstarct: A city gate natural pressure drop station (CGS) has different items and one of the most important of them is gas heater. natural gas temperature depends to it’s pressure, it’s pressure is reduced during CGS, and also temperature drop is limited by hydrat forming. In order to prevent natural gas temperature approaches to this temperature, so in this regard heater is very necessary for CGSs. At the moment, it’s done by line heaters that use natural gas as their original fuel. Consuming of high amount of fuel is the main problem by these kinds of heaters. In this thesis, feasibility of employing solar energy to heat flow gas before the pressure drop action in order to reducing fuel consumption by the heaters is done. In this research, first pay attention to weather conditions of Sari and also reachable solar heat flux by using theoretical methods is calculated. In optimum system design phase, two different scenarios emerge. First, the heater is smart and controllable. Second, the heater isn’t smart and its uncontrollable. It means the heater wont can react to In this wise the heater will be able to react to required variations on thermal energy. In each states, the optimum collector module will choose. Finally economical survey will be on each system. This research has done on Akand station in Sari and required data has provided by Sari weather bureau.