At a glance
EEXI — the design-efficiency index
EEXI (Energy Efficiency Existing Ship Index) is the existing-fleet counterpart to EEDI, which has applied to newbuildings for years. It is a one-time, design-based measure: a ship calculates its attained EEXI from its design parameters and must show it meets a required value for its type and size. Compliance is certified once and recorded on the International Energy Efficiency Certificate (IEEC). Many existing ships meet EEXI through engine power limitation (EPL) or shaft power limitation, which caps installed power and, in effect, top speed.
Key point
EEXI is a paper/design gate, not an operational one. A ship either clears it or is modified until it does. It does not change year to year — unlike the CII.
CII — the annual operational rating
The Carbon Intensity Indicator is where operations, and fuel, actually bite. Each ship above 5,000 GT calculates its attained CII — broadly, CO₂ emitted per unit of transport work (grams of CO₂ per deadweight-tonne-mile for most cargo ships) — over the calendar year, using its IMO Data Collection System fuel data. That attained value is compared against a required value and the ship is given a rating from A (best) to E (worst).
The reduction factor
The required carbon intensity gets stricter each year. The annual reduction factor runs at roughly 2% per year against the 2019 reference line through 2026. The factors for 2027 to 2030 are being decided through an IMO review of the scheme — stricter numbers are widely expected, so a ship that is a comfortable C today can slide toward D as the line drops beneath it.
A ship rated D for three consecutive years, or E in any single year, must develop a corrective action plan as part of its SEEMP (Ship Energy Efficiency Management Plan) and have it approved. There is no direct IMO fine — but charterers, lenders, cargo owners and some ports increasingly screen on CII rating, so a weak rating is a commercial problem well before it is a regulatory one.
The 2026 review
The CII framework was always designed to be reviewed and strengthened. That review — covering the reduction factors beyond 2026, the rating boundaries, and how well the metric captures real-world efficiency — is running now and is expected to sharpen the trajectory. Operators planning fleet deployment and fuel strategy for the late 2020s should assume tighter, not looser, requirements.
What it means for bunker buying
Because CII is CO₂ per transport work, it is directly sensitive to the fuel you burn. Switching part of the fuel mix to a certified biofuel blend or to LNG reduces the CO₂ numerator and improves the rating; so does slower steaming and routine efficiency work. This is where CII, the EU’s EU ETS and FuelEU Maritime rules, and the forthcoming IMO Net-Zero Framework all point the same way: lower-carbon fuel is no longer only a fuel-price decision, it is a compliance decision. Seven Ocean can advise on biofuel blend availability and documentation at the ports where you bunker.
Frequently Asked Questions
Which ships does CII apply to?
Cargo, RoPax and cruise ships above 5,000 GT — the same band that reports under the IMO Data Collection System. EEXI applies more widely, to existing ships above 400 GT.
What happens if a ship gets a D or E rating?
D for three consecutive years, or E in any single year, requires an approved corrective action plan in the SEEMP. No direct IMO fine, but charterers, financiers and ports increasingly screen on rating.
Does the fuel I burn affect my CII?
Yes. CII is CO₂ per transport work, so certified biofuel blends and LNG lower the CO₂ numerator and improve the rating. Slower steaming and efficiency measures help too.
Is the CII scheme getting stricter?
Yes. Roughly 2% per year through 2026, with 2027–2030 factors set by an ongoing IMO review. Stricter factors are widely expected.
How is CII different from EEXI?
EEXI is a one-time, design-based index — pass once. CII is an annual, in-service rating that gets stricter every year and depends on how the ship is actually operated and fuelled.