A flaw in the ice-class calculation methodology used under FuelEU Maritime has left compliant shipping operators facing potential penalties running into tens of millions of euros. The error was embedded in the European Maritime Safety Agency (EMSA)'s Thetis compliance system and widely adopted by third-party verifiers.
The error affected how energy consumption — and therefore emissions intensity — is calculated for ice-class vessels. The wrong formula produced 'paper non-compliance' that diverged from the ships' real-world performance. Operators saw compliance in their own reporting systems while Thetis output flagged them as non-compliant.
The FuelEU Maritime regime has been in force since 2025, requiring vessels in EU waters to gradually reduce average annual energy intensity. With penalties tied to a high rate per tonne of CO2 equivalent, the operational impact is material.
Industry representatives say EMSA must, having acknowledged the flaw and corrected the methodology, set out how retroactive revisions will be handled. Verification firms may need to reprocess data for the 2025 reporting year.
The episode is an important warning about how software and methodology errors in complex climate regulation can produce direct financial exposure for individual operators. The industry is amplifying calls for auditable calculation infrastructure and independent verification mechanisms.
Key Takeaways:
1. An ice-class calculation flaw was identified in EMSA's Thetis system.
2. The error showed compliant vessels as non-compliant, creating millions in penalty exposure.
3. FuelEU Maritime has been in force since 2025 with high per-tonne CO2e penalty rates.
4. Verifiers may need to reprocess 2025 reporting-year data.
5. The episode strengthens calls for auditable calculation infrastructure and independent verification.
