Considering the vast amount of parameters that affects the pressurisation pathway, we present a rigorous modelling framework that is flexible and can handle any combination of parameters, like inlet/outlet pressure, pressurisation pathway (compression only or compression, cooling/liquefaction and pumping), cooling temperatures, pressure drop in compression stages, different number of compression stages, all based on open source software. In addition, an integrated approach for estimating equipment and total plant costs that relies on methods and databases openly available and documented is described and applied. Thus, the presented tool does not rely on proprietary closed source black-box models or databases for full transparency and clarity.