What are EEDI and EEXI and how do they influence vessel design and retrofit decisions?

• A. EEDI is Energy Efficiency Design Index for new ships; EEXI is Energy Efficiency Existing Ship Index; they set emission intensity targets to drive design and retrofit choices.
• B. EEDI is Economic Efficiency Development Index; EEXI is Environmental Evaluation Index.
• C. EEDI and EEXI are unrelated to ship design.
• D. EEDI and EEXI are port fees.

Answer: (A)

Pushing ships to be more energy efficient is the core idea. EEDI and EEXI are IMO rules that set targets for how CO2-intensive a ship’s operation can be, measured as emission per unit of transport work.

EEDI, or Energy Efficiency Design Index, applies to new ships. It requires the vessel’s design to meet a lower CO2-per-transport-work standard at a given service speed. Because the target tightens over time, designers must incorporate efficiency improvements from the outset—better hull form and propulsion, smarter engines, and ways to reduce power without hurting performance. This shapes choices like engine type and size, hull shape, propeller design, and the use (or avoidance) of energy-saving technologies to ensure the ship is compliant when it is built.

EEXI, or Energy Efficiency Existing Ship Index, applies to ships already in service. It sets a minimum energy-efficiency level for those vessels and can be met through retrofits or operational changes. Compliance might come from hull and propeller improvements, energy-saving devices, waste-heat recovery, shaft generators, or even adjusting operating speeds. If retrofits aren’t feasible or cost-effective, operators may need to alter speeds or voyage patterns to stay within the standard.

Together, they influence decisions on both new-build design and retrofits: you design with the target in mind for the lifetime of the ship, and you plan and invest in upgrades for existing fleets to meet the required efficiency levels.