What is EEXI and how does NavCad help with compliance assessment?

What is EEXI

The Energy Efficiency Existing Ship Index is an IMO regulation (MEPC resolution) that assigns a mandatory energy efficiency rating to existing ships. The EEXI score quantifies the CO2 emissions per unit of transport work. Ships that exceed the required EEXI threshold must implement corrective measures typically an engine power limiter before they can trade.

EEXI applies to commercial vessels of 400 gross tons and above across all main vessel categories (bulk carriers, tankers, container ships, ro-ro, passenger vessels, and others). The calculation requires an accurate speed–power curve based on the vessel's installed engine, transmission, and propeller at the summer load line.

NavCad's EEXI Assessment Utility

NavCad's EEXI Assessment utility (Tools | Utilities | EEXI Assessment, Premium Edition) automates the IMO MEPC calculation sequence within a NavCad project. The utility:

• Calculates the EEXI Score from the vessel's speed–power curve, installed MCR, and engine limiter setting.
• Investigates how design changes affect the score engine limiters, propeller pitch changes, hull modifications such as bulbous bow additions.
• Identifies the EEXI reference speed, defined by the intersection of the propeller power demand curve with the reference power line.
• Generates an EEXI Technical File document for QA review and future compliance benchmarking.

Recommended Workflow

• Prepare a NavCad project for the vessel at summer load line condition with fully populated hull, propulsor, and engine data.
• Use aligned prediction for the speed–power curve where model test or sea trial data is available this produces the highest fidelity EEXI input.
• Run the EEXI Assessment utility, entering the vessel category, LPP, and breadth.
• Review the EEXI score relative to the required threshold for the vessel type and size.
• If the score exceeds the threshold, use the utility to investigate compliance options (engine limiter, propeller change, hull modification) before finalizing the Technical File.

Design-Stage Use

The EEXI Assessment can also be used at the design stage to investigate compliance before final submittal. Evaluating engine limiter options, propeller repitching, or hull modifications in NavCad provides a quantitative basis for the compliance decision, reducing the risk of regulatory surprises after the vessel is in service.

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