The study was conducted as part of the notification procedure with the European Commission for the assessment of the aid scheme "Early Scaling-up of the Energy Transition for Seagoing Vessels 2026–2030" under the European State aid rules. As part of this procedure, the European Commission requested four Total Cost of Ownership (TCO) calculations to provide insight into the break-even points at which shipowners would have sufficient incentive to invest in cleaner vessels without subsidy support.