Decarbonisation regulation has moved from the conference agenda to the work list. For owners of existing tonnage, the question is no longer whether to engage with EEXI and CII, but how to bring an already-built ship into compliance without writing off her remaining trading life. Retrofitting is the answer that protects the asset: instead of replacing a vessel, you upgrade her propulsion, energy and emissions systems to meet the rules and run more efficiently against them.
The pressure is twofold. Regulation rarely stands still, and the commercial case for cutting fuel and emissions stands on its own even where the rules do not yet bite. A well-scoped retrofit serves both - and the difference between a project that pays for itself and one that simply costs money usually comes down to how it was specified, approved and timed.
EEXI and CII are different problems
It helps to be clear that the two regimes ask different questions, and a retrofit programme has to answer both.
- EEXI (Energy Efficiency Existing Ship Index) is a one-off design measure. It asks whether the ship, as designed, is efficient enough on paper. It is met once and certified, and the most common route to compliance is technical rather than operational.
- CII (Carbon Intensity Indicator) is an annual operational measure. It rates the ship on the carbon she actually emits per unit of transport work over a year, and the rating tightens over time. A ship can be EEXI-compliant and still slide down the CII bands if her real-world efficiency does not improve.
The practical consequence is that EEXI can often be closed with a single intervention, while CII rewards a programme of efficiency gains that compound over the vessel’s service life. The best retrofit projects treat the two together rather than chasing a certificate and ignoring the operating reality.
The retrofit toolkit
There is no single decarbonisation retrofit. The right package depends on the hull, the trade and the regulatory shortfall, but the common interventions fall into a few families.
Closing the EEXI gap
- Engine power limitation (EPL or ShaPoLi). Capping available shaft power is frequently the most cost-effective way to bring an existing ship into EEXI compliance, with the limitation engineered, sealed and documented for verification.
- Energy-saving devices. Pre-swirl and propeller-boss-cap fins (PBCF), wake- equalising and flow-improving appendages recover propulsive efficiency that the index credits directly.
Improving real-world carbon intensity for CII
- Propeller and bulbous-bow modifications matched to the ship’s actual loaded and ballast operating points, rather than her original design condition.
- Shaft generators that shift electrical load off the auxiliary engines and onto the more efficient main plant.
- Pump and auxiliary optimisation, variable-speed drives and LED lighting - unglamorous, but each one trims the daily fuel burn that CII measures.
Many of these also sit alongside the wider environmental retrofits owners are already weighing - ballast water treatment systems and exhaust scrubbers - so it is worth scoping them as one campaign rather than a series of disruptive visits.
Keep the modification class-approved
A decarbonisation retrofit is a permanent change to the vessel’s machinery or structure, and that means it lives or dies on approval. Engine power limitation has to be verifiable; an appendage or propeller change alters loads and must be calculated and accepted; an EPL or CII-driven modification has to be reflected in the ship’s certificates and technical file.
This is exactly where projects come unstuck. Hardware gets installed, then class or flag queries the calculations, and the vessel is left with an unapproved modification and a compliance gap she thought she had closed. The disciplined route is to prepare the modification package - drawings, calculations and the basis of the limitation - and get it through class and flag before steel is cut or seals are fitted, so installation is the last step in an approved chain rather than the first gamble.
Time it around the trading pattern
The other way retrofit value leaks is downtime. A vessel does not earn while she is out of service, and a poorly sequenced retrofit can cost more in off-hire than it saves in fuel. The aim is to deliver the change without disrupting the trading pattern any more than necessary - scheduling installation into a planned dock window where one exists, and phasing work that can be done alongside so the ship keeps earning.
This is why feasibility comes first. Assessing the vessel, the regulatory driver and the payback case up front tells you not only which option to choose, but when to do it - so the most cost-effective technical answer is also the most cost-effective schedule. ShipSmith manages retrofit and upgradation from that feasibility study through engineering, class approval, procurement, installation and commissioning, including crew familiarisation on the new system once it is aboard.
The takeaway
EEXI and CII are not a single hurdle to clear but an ongoing standard to operate against, and existing tonnage can meet them. The owners who come out ahead are the ones who treat decarbonisation as a managed engineering project: scope the EEXI gap and the CII trajectory together, choose interventions by payback rather than fashion, get every modification approved before it is installed, and fit the work into the trading calendar. Done that way, a retrofit is not a regulatory cost - it is an investment that extends the trading life and protects the value of the ship.