The transition away from fossil fuels in the energy sector is accelerating with the increasing integration of renewable energy sources (RES) such as wind and solar photovoltaics (PV). However, these renewable sources introduce significant challenges, particularly in maintaining a constant balance between energy production and demand due to their intermittent nature. One promising solution lies in long-term energy storage by Power-to-X-to-Power (PtXtP), which allows surplus electricity from high-production periods to be used to produce a new energy carrier (X), which can then be used to produce electricity during low-production periods. This approach is particularly important for addressing seasonal imbalances, such as excess summer production and higher winter demand. Reliance on such systems should be avoided as much as possible, as PtXtP technologies are associated with high cost due to low round-trip efficiency (<35%). Hydrogen is widely considered as a medium for storing excess electricity, but alternative energy carriers such as synthetic natural gas and methanol may be more advantageous under certain conditions. Simultaneously, increasing interest is being given on importing massive quantities of hydrogen-based fuel in Europe. This work investigates the impacts of hydrogen-based fuel imports versus domestic production on the need for flexibility of the energy system. The analysis uses EnergyScope TD, a linear programming-based optimization tool designed to model the whole energy system, including heat, electricity, transport, and industry. Additionally, the study is extended to a European-scale model to assess the impact of geographical diversity on renewable energy potential and, hence on the need for flexible electricity generation. This study suggests that transitioning the transport and chemical sectors from fossil fuels to e-fuels or e-bio-fuels reduces the reliance on flexible power generation technologies such as combined cycle gas turbines (CCGT). Specifically, substituting renewable fuel domestic production with import increases electricity generation requirements for flexibility by 0.24 MWhCCGT/MWhfuel, for Sustainable Aviation Fuel (SAF). Sustainable fuel import also increases the need for energy storage through gas and the need for e-bio-methane production. Several parameters are studied to understand the conditions under which these effects of increasing sustainable fuel import are valid. These parameters are: the share of nuclear in electricity generation, the type of technology producing the electricity, the maximum allowed hydrogen storage, the type of imported energy carrier, the flexibility of electrolyzers, and the interconnection between different regions in Europe.