Results of trade-off studies aiming to compare different ship power and propulsion configurations inherently contain uncertainty. This is true for both the technical part and for the financial part of the trade-off study. The technical part typically includes the system characteristics of the vessel as inputs, resulting in predicted fuel consumption and emissions at various ship speeds. Fuel consumption numbers subsequently feed into the financial part of the analysis which typically includes prices of equipment, fuel prices or fuel price scenarios, the discount factor and other aspects such as the operational profile which plays an important role in the trade-off study. Finally, financial KPI’s such as Net Present Value and payback period can be compared between different power and propulsion concepts, thereby supporting decision makers in the selection of a specific configuration or retrofit. In this paper, the effect of uncertain input parameters on both the intermediate technical output and on the financial KPI’s is demonstrated by means of a case study. The study shows that the uncertainty associated with relevant KPI’s is sufficiently large to warrant further investigation beyond accepting model predictions as completely accurate, particularly when conducting techno-economic trade-off analysis of ship power and propulsion configurations. In the broader context, consideration of uncertainty is a must for statutory and regulatory authorities in the formulation of policy.@en