Relying on cost/kWh as the primary metric for evaluating maritime energy storage systems is misleading, incomplete and outdated. Although this metric may appear straightforward, it ignores critical factors that significantly affect the total cost of ownership, long-term performance, project sustainability and vessel lifespan. A proper evaluation must go beyond the initial cost per kWh and address the key drivers of battery system costs: cost per cycle, scope of supply, system impact on ancillary equipment, capex versus opex balance, and decommissioning, removal and recycling costs.