Abstracy. The purpose of this study is to provide an analysis of the comparison and impact of changes in the model of Gas Transportation Tariff calculations through Pipes on the transportation of natural gas for fuel power plants in the region X. Which initially used a single tariff distance system that provides gas prices that are still not economically attractive, will be replaced with a more efficient multi-tariff postage stamp system. With the change of tariff calculation method, it will get the lower gas price and will inevitably increase the commercial appeal to be able to replace HSD (High-Speed Diesel) Generator which is expensive and cause more pollution. Initially, the substitution program is still less attractive because gas prices are still inefficient because the use of tariff calculation method is less precise. New tariffs are modeled by modifying cash flow and some variables with scenarios dividing tariffs into groups and re-modeling the volume of gas flowing in the pipeline through simulations using software and calculations. With the sensitivity test will also be done to provide the best scenarios to the efficiency of gas price formation. If gas prices are more efficient than fuel, it will further increase the attractiveness to accelerate fuel substitution of fuel with cleaner gas fuel and support Government programs. A comparison of the carbon decline will also be made to prove the substitution of diesel with gas to have a positive impact on the environment to provide an analysis of environmental issues. Finally, we propose that the application of a multi-tariff system will provide the best scenario for enhancing the efficiency of natural gas prices in the substitution of power generation from diesel into previously less attractive gas to be more efficient and more environmentally friendly.