This study suggested the optimum vapor pressure for an LPG carrier with pressure vessels as cargo tanks. A new pressure vessel, the lattice pressure vessel (LPV), was adopted to improve the volume efficiency of the LPG carrier. An economic evaluation was conducted to find the optimum vapor pressure of the proposed tanks. The proposed storage tank had the combined advantages of the IMO Type A tank and Type C tank. For economic evaluation, the affected components in the LPG carrier were identified and estimated when the proposed storage tank was applied to the containment system of the conventional LPG carrier. The cargo tank was designed in accordance with the detail specifications regarding the vapor pressure. The economic evaluation indicated that the optimum vapor pressure should be 4 bar. It was shown that the material selected carbon steel of the tank was an effective item. Although the results of this study have somewhat uncertainty that the storage facility was adapted the operating condition of the proposed LPG carrier in the design stages, it provides useful information for developing the LPG supply chain based on high-pressure LPG carriers.