Hull and propulsion efficiency measures range from engine power limits and slow steaming to bulbous bow and propeller retrofits, premium coatings, hull cleaning and weather routing. Verified data favour bow and propeller packages at 14-18% in model tests, while DNV puts the fleet-wide potential at up to 16% by 2030.
What it is and how it works
Hull and propulsion efficiency measures are the layered toolkit for cutting fuel on existing ships without changing the fuel. The first layer is power management: engine power limitation and shaft power limitation, which Kongsberg implements by altering the RPM setpoint on fixed-pitch, electronically controlled engines or the pitch setpoint on controllable-pitch installations (Kongsberg), together with slow steaming. The second is one-off hydrodynamic retrofits: a bulbous bow redesigned for the slower speeds ships actually sail, a propeller redesign and devices such as boss cap fins. The third is surface condition: premium antifouling coatings and scheduled hull cleaning. The fourth is operational: performance monitoring, digital twins and weather routing.
Why it matters now
CII and European carbon costs fall mainly on existing tonnage, and the IMO Net-Zero Framework approved at MEPC 83 brings greenhouse gas requirements from 2028. DNV's Maritime Forecast to 2050 (2025 edition) puts the efficiency potential at up to 16% of fuel use by 2030, worth about USD 23 billion a year including speed reduction, with 25-28% lower energy use than business as usual by 2050, up to 1,700 vessels needing upgrades around 2030, and a large share of the potential already cost-effective (Biofuels Digest). Clarksons counts energy saving technologies on 14,189 ships, 46.1% of fleet tonnage, and modern eco vessels at 37.0% of tonnage at the end of 2025 (Cyprus Shipping News).
Key players and products
DNV, Lloyd's Register and ABS act as verifiers and publish the most defensible retrofit data; DNV's Abatement Insights database covers more than 50 measures, though its rankings are not public. Hempel, Jotun and AkzoNobel supply coatings, with only Hempel's figures surfacing in this research. Syroco and Sofar Ocean sell routing and digital twins; Neptune Robotics offers robotic hull cleaning; FORCE Technology, MARIN and HSVA run the model tests behind bow and propeller retrofits. Kongsberg supplies ShaPoLi hardware.
Figures that matter
| Metric | Value | Source type | Source |
|---|---|---|---|
| Fleet efficiency potential by 2030 | up to 16%, about USD 23 bn/yr | aggregator | DNV via Biofuels Digest |
| EEXI compliance by EPL/ShaPoLi, container ships | about 17.3% calculated CO2 cut, about 10% lower speed | verified | TRID |
| Real-world 2030 effect of EEXI alone | 0.7-1.3% | verified | ICCT |
| Bulbous bow redesign, HMM 8,600 TEU | almost 1,000 t/yr, USD 680,000 | verified | DNV |
| 13,100 TEU bulb plus propeller | 6.5% plus 7.5%, 18% combined in model tests | verified | MarineLink |
| DNV bow, propeller and boss cap fin package | about 16%, USD 2.35 m, NPV USD 2-10 m | verified | DNV via Maritime Professional |
| Hempaguard X7 and MaX out-of-dock gain | 6% and 8% | vendor | Hempel |
| Optimised hull cleaning timing | up to 5% over four years | verified | arXiv |
A study of existing container ships found EEXI compliance relied mainly on EPL and ShaPoLi, giving an average calculated CO2 reduction of about 17.3% while calculated speed fell about 10%; propeller retrofits cut shaft power without losing speed (TRID). ICCT counters that 2019 engine loads were typically 38-50% MCR while EEXI allows 65-77%, so EEXI alone would cut 2030 fleet CO2 by only 0.7-1.3% (ICCT). One-off retrofits deliver more: DNV data show a redesigned bulbous bow gives 5% or more, with the first converted HMM 8,600 TEU ship saving almost 1,000 t a year for USD 680,000; a 13,100 TEU ship combined a 6.5% bulb and a 7.5% propeller gain for 18% in independent model tests, and a Seaspan 8,500 TEU project reached 14% (MarineLink). DNV's USD 2.35 million bow, propeller and boss cap fin package cuts fuel about 16% with an NPV of USD 2-10 million by 2038 depending on fuel price (Maritime Professional). Hempel's 6% for Hempaguard X7 and 8% for Hempaguard MaX out of dock are vendor claims. A University of Southampton study finds optimised cleaning timing saves up to 5% over four years (arXiv). Syroco claims about 10% from routing; DNV verified its methodology but no figure, noting that no recognised standard exists for the counterfactual voyage.
Developments 2023-2026
- Wallenius Wilhelmsen's PCTC bulb retrofits average about 6%, up to 30% at low draught and speed (Clean Shipping International).
- Neptune Robotics claimed in May 2026 an average 18% saving from robotic cleaning plus AI routing, up to 34% after one cleaning cycle, a vendor figure (Digital Ship).
- DNV's chief executive argued in 2026 for efficiency measures first, while noting an 18-year payback on a VLCC shaft generator retrofit at February 2026 fuel prices of about USD 670/t.
Outlook
Ranked by return, operational measures come first per dollar but depend on the counterfactual; bow and propeller packages give the largest verified step for slow-steaming-era container ships; premium coatings add 6-8% out of dock and decay between dockings; and engine power limits serve mainly paper compliance unless they bite below actual loads. DNV's own examples vary widely, so vessel-specific modelling is essential.
