Ship Energy Efficiency : EEXI and CII Regulation Awareness

Introduction to MARPOL Annex VI Amendments

On June 17, 2021, during the 76th session of the International Maritime Organization‘s Marine Environment Protection Committee (MEPC 76), significant amendments to MARPOL Annex VI were adopted. These amendments introduce new regulations aimed at enhancing the energy efficiency of existing ships and reducing greenhouse gas emissions from international shipping. Specifically, the amendments include the introduction of the Energy Efficiency Existing Ship Index (EEXI) and the Carbon Intensity Indicator (CII), which are set to enter into force on November 1, 2022. This article provides a comprehensive overview of these regulations, their implications for the maritime industry, and guidance on compliance.

Amendments to the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex VI entered into force on 1 November 2022. Developed under the framework of the Initial IMO Strategy on Reduction of GHG Emissions from Ships agreed in 2018, these technical and operational amendments require ships to improve their energy efficiency in the short term and thereby reduce their greenhouse gas emissions. From 1 January 2023 it became mandatory for all ships to calculate their attained Energy Efficiency Existing Ship Index (EEXI) to measure their energy efficiency and to initiate the collection of data for the reporting of their annual operational carbon intensity indicator (CII) and CII rating.

EEXI and CII: A Practical Guide for Maritime Professionals

Updated to 15 October 2026

Energy efficiency is now part of everyday ship operation. Engineers monitor fuel use and machinery performance; deck officers plan routes and record distance travelled; and both departments contribute to the data used to assess a ship’s carbon intensity. Two important requirements under MARPOL Annex VI are the Energy Efficiency Existing Ship Index (EEXI) and the Carbon Intensity Indicator (CII). They address different questions:

The amendments introducing these measures entered into force on 1 November 2022, and their requirements began to apply on 1 January 2023. The first CII ratings, based on 2023 operations, were issued in 2024.

Energy Efficiency Existing Ship Index (EEXI)

EEXI estimates the technical efficiency of an existing ship using characteristics such as its capacity, propulsion power, fuel-related CO₂ emissions and reference speed. The ship’s attained EEXI must be no greater than its required EEXI, which depends on ship type and size. Think of it as a check on the ship’s technical design and approved configuration. It is not a yearly score based on the fuel burned during voyages.

The commonly stated threshold of 400 gross tonnage (GT) and above needs a qualification: EEXI applies to ships in the categories specified by MARPOL Annex VI, including bulk carriers, tankers, container ships, gas and LNG carriers, general cargo ships, refrigerated cargo carriers, certain ro-ro ships and cruise passenger ships. The threshold does not mean that every vessel of 400 GT or more has an EEXI calculation. CII has a different threshold, discussed below.

For ships already in service, EEXI compliance was verified at the first applicable annual, intermediate or renewal survey, or an applicable initial survey, on or after 1 January 2023. A major conversion may require the EEXI to be recalculated and verified again. The supporting calculation is documented in the ship’s EEXI Technical File.

A ship may meet its required EEXI through an approved combination of measures, such as propulsion improvements, energy-saving devices or an engine power limitation (EPL) or shaft power limitation (ShaPoLi) system. Cadets should understand an important safety point: a power limit is part of an approved arrangement with procedures governing the use of a power reserve. It must not be treated as an informal instruction to withhold power when the ship needs it for safety.

–

Carbon Intensity Indicator (CII)

CII measures annual operational carbon intensity. It generally applies to ships of 5,000 GT and above in the specified MARPOL Annex VI ship categories. The ship collects operational data throughout the year, but its official attained CII and rating are calculated and verified after the calendar year ends. A dashboard may show an estimated rating during the year; that estimate is useful for management, but it is not the verified annual rating.

In simplified terms, the main CII calculation relates the ship’s annual CO₂ emissions from fuel consumption to its capacity multiplied by distance travelled. Capacity is generally expressed as deadweight tonnage (DWT) for cargo ships and GT for the relevant passenger and ro-ro ship types. This capacity-based measure is a proxy for transport work: it does not mean that every voyage carried a full cargo. The applicable IMO calculation guidelines also provide rules for particular ship types, correction factors and voyage adjustments.

Classroom example: Suppose a tanker emits 6,000 tonnes of CO₂ in a year, has a capacity of 50,000 DWT and travels 30,000 nautical miles. Its simplified indicator would be:

Example: Suppose a tanker emits 6,000 tonnes of CO₂ in a year, has a capacity of 50,000 DWT and travels 30,000 nautical miles.

CII = annual CO₂ emissions ÷ (ship capacity × distance travelled)

CII = 6,000,000,000 g CO₂ ÷ (50,000 DWT × 30,000 nautical miles) = 4 g CO₂ per DWT-nautical mile

The 6,000 tonnes of CO₂ are converted to grams so that the result is expressed in grams per DWT-nautical mile. This simplified result does not, by itself, establish the ship’s A–E rating.

This example shows the units and principle only. A value of 4 does not, by itself, establish a CII grade: the grade requires the applicable ship-type reference line, reporting-year requirement and any permitted adjustments.

How the A–E rating works

The verified attained annual CII is compared with the applicable required annual CII and rating boundaries. The resulting grade is A, B, C, D or E, with A representing the best performance and C representing moderate performance. The rating appears on the ship’s Statement of Compliance associated with fuel consumption reporting and operational carbon intensity.

A ship rated D for three consecutive years, or E for one year, must develop a ship-specific corrective action plan in its Ship Energy Efficiency Management Plan (SEEMP), have the revised plan verified and carry out the planned actions. A D rating in a single year does not automatically trigger that particular corrective-plan requirement.

For a normal full calendar-year reporting cycle, the attained CII is reported within three months after year-end. Following verification, the Statement of Compliance is issued no later than five months from the beginning of the new calendar year.

–

Where the SEEMP fits

The Ship Energy Efficiency Management Plan (SEEMP) turns these requirements into shipboard procedures. Its three parts have different purposes:

Part I applies to ships of 400 GT and above within its scope. Parts II and III concern ships meeting the relevant 5,000 GT requirements; Part III applies to the specified CII ship types. The SEEMP is therefore more than a document kept for inspection: it should explain how the crew and company collect reliable data and improve performance.

What changed in 2025 and 2026?

Stricter CII requirements through 2030. At MEPC 83 in April 2025, IMO adopted updated CII reduction factors relative to the 2019 reference line. These are 11% for 2026, 13.625% for 2027, 16.250% for 2028, 18.875% for 2029 and 21.500% for 2030. These percentages describe the tightening required CII reference, not a promise that each individual ship will cut its total fuel consumption by that percentage.

Clarified distance data. At MEPC 84 in May 2026, IMO amended the CII calculation guidelines and SEEMP guidance to clarify the use and reporting of total distance travelled, including distance while the ship is under way and while it is not under way. The guidance continues to use capacity multiplied by distance as the proxy for an individual ship’s CII calculation; newly reported actual transport-work data may be analysed as IMO reviews the framework. Accurate definitions and consistent records therefore matter.

Further review is underway. IMO completed the first phase of its review of EEXI, CII and SEEMP and is conducting a second phase planned to run from 2026 to 2028. Possible refinements to metrics and the SEEMP framework should be described as work under consideration until they are adopted. The separately proposed IMO Net-Zero Framework, involving a marine fuel standard and GHG pricing, had been approved as draft text, but its adoption discussions were adjourned; it is not an EEXI or CII rule already in force as of 15 October 2026.

What should a cadet look for on board?

A cadet can connect the regulations to actual shipboard work by asking to see the SEEMP, the relevant International Energy Efficiency Certificate and EEXI Technical File, and the latest Statement of Compliance. With the supervising officer’s guidance, compare the fuel figures in logs and reporting systems, observe how distance and voyage data are recorded, and ask how the ship checks for missing or inconsistent entries.

During operations, notice how voyage planning, weather routing, hull and propeller condition, machinery maintenance, generator loading and unnecessary auxiliary demand affect fuel use. These are practical ways to improve efficiency, but every proposal must still meet the ship’s safety, navigation and operational needs. An accurate report and a well-run ship both matter: EEXI establishes a technical standard, while CII shows how the ship performed over the year.

–

Shipowners and Operators

• Compliance Requirements: Shipowners must ensure that their fleets comply with EEXI and CII regulations by developing strategies for retrofitting or modifying vessels as necessary.
• Operational Adjustments: Operators will need to adjust operational practices to improve carbon intensity ratings and meet performance benchmarks.

Technical Superintendents and Ship Managers

• Implementation Planning: Technical superintendents are tasked with developing timelines for compliance and ensuring that all necessary modifications are executed efficiently.
• Training and Awareness: There is a need for training staff on new operational practices related to energy efficiency and carbon intensity monitoring.

Flag State Surveyors

• Regulatory Oversight: Flag state surveyors will play a critical role in verifying compliance with EEXI and CII requirements during inspections.
• Documentation Review: Surveyors must be familiar with the documentation required for demonstrating compliance.

Consultants and Ship Designers/Builders

• Advisory Role: Consultants will be essential in advising shipowners on compliance strategies, including potential retrofitting solutions.
• Design Innovations: Ship designers may need to innovate new designs that inherently comply with EEXI standards for future vessels.

–

Relationship Between EEDI, EEXI, and SEEMP

Understanding the relationship between various efficiency indices is crucial for effective compliance:

• Energy Efficiency Design Index (EEDI): This index applies to new ships, setting mandatory energy efficiency standards based on design. In contrast, EEXI focuses on existing vessels.
• Ship Energy Efficiency Management Plan (SEEMP): The SEEMP is enhanced under the new regulations to ensure ongoing operational improvements in energy efficiency. It serves as a management tool that outlines how a vessel will achieve its energy efficiency goals.

Future Implications

The amendments to MARPOL Annex VI signal a significant shift towards greater accountability in reducing greenhouse gas emissions from shipping. As these regulations take effect, it is expected that:

• Increased Scrutiny: Regulatory bodies will increase scrutiny on compliance efforts, leading to potential penalties for non-compliance.
• Market Competitiveness: Vessels that successfully comply with EEXI and CII standards may gain competitive advantages in markets increasingly focused on sustainability.
• Technological Advancements: There will likely be an acceleration in technological advancements aimed at improving vessel efficiency and reducing emissions.

The adoption of the EEXI and CII regulations under MARPOL Annex VI represents a critical step towards achieving sustainability goals within the maritime industry. Stakeholders must proactively develop compliance strategies to navigate this evolving regulatory landscape effectively. By understanding these new requirements and their implications, shipowners, operators, and other maritime professionals can position themselves for success in an increasingly environmentally conscious market. Upon successful completion of relevant training courses focused on these amendments, participants will receive certification recognizing their competence in implementing these essential regulations.