The results here presented are valid for a completely autarchic system. Unfortunately, due to the large surface required for electricity production from PV, it may occur that a complete self-production of H2 is unfeasible. In this case, part of the electricity should be purchased from other suppliers of renewable energy. This electricity would be subject to a grid use fee, which is here set to 0.05 €/kWh (the average value in Switzerland). Figure shows how the use of external electricity would change the cost of the final product. The cost of the final product increases linearly with the decrease of the degree of self-sufficiency, reaching high values for a system purchasing 100 % of the electricity. The slope of the lines is higher to produce H2, as in this case more electricity needs to be purchased. These results show that the boundary conditions in terms of availability of renewable energy and the policies in terms of grid use have a substantial influence in the economic performance of the PtX system. It is therefore essential to check carefully the local boundary conditions of the location where the hypothetical PtX plant would be located prior to extrapolating the results of this research paper. Figure Sensitivity analysis of the cost of the final products according to the degree of self-sufficiency achievable. With degree of self-sufficiency is intended the fraction of electricity that is produced by own PV system, while the rest has to be purchased from the grid (including payment of grid fees).