The challenges and risks brought by the new 2020 sulfur cap are undeniable. Since the idea of using Liquefied Natural Gas (LNG) as a marine fuel for ocean-going ships has become more attractive to the industry, in this study, a lifetime-based cost evaluation framework is proposed to systematically evaluate the implementation of using LNG as fuel for general ocean-going commercial ships. This approach can be represented as a quantitative decision-supporting process with a combination of very different features of the economic aspect in one coherent framework. The benefits of the approach are discussed through a case study, and the economic performance of the 3 varying sizes of ocean-going LNG-fueled container ships are tested. The case study results indicate that, considering the differences in the life cycle cost (LCC) and cash flow performances between LNG-fueled ships and conventional oil-fueled ones, the acquisition premium for ocean-going LNG-fueled container ships is sufficient to warrant the saving in terms of the LCC. However, the LNG price differences in the different regions could lead to noticeable differences in LCC results. This study’s analysis fills gaps identified in the existing research about the benefits and disadvantages of using LNG as fuel for general ocean-going commercial ships. Finally, the study reveals an underlying novelty of the proposed framework to provide reliable decision supporting in investment by expanding the short-term perspective to a lifetime one.