Hull cleaning fuel savings: what fouling costs a year
A fouled hull and propeller need more power for the same speed. Enter the power increase your monitoring shows, and see the fuel, the EU ETS allowances and the FuelEU cost it adds, and how fast a cleaning pays back.
Updated 2026-10-28
Calculate
The arithmetic
Extra fuel = main-engine fuel × increase ÷ (100 + increase). Each extra tonne costs its price, plus its CO₂ (3.114 t per tonne of heavy fuel oil) × the allowance price × the EU share, plus its FuelEU deficit at the pool price on the EU share. The payback is the cleaning cost divided by the daily cost of the fouling.
Measuring it properly
The power increase is the uncertain part. The hull performance tool fits the sea-trial speed-power curve, keeps only steady, fair-weather records, and tracks speed loss and power increase between cleanings and dry-dockings, following ISO 19030. Every rejected record keeps its reason.
Questions
How much fuel does hull fouling waste?
At a given speed, main-engine fuel rises with the power needed, so a power increase of p% wastes p/(100+p) of the main-engine fuel. A 10% increase wastes about 9%.
How do I know my ship's power increase?
From performance monitoring: noon reports or sensor data compared with the sea-trial speed-power curve, filtered for weather and draft, as ISO 19030 describes. The app does this from a noon-report file.
Does fouling raise EU ETS and FuelEU costs?
Yes. Every extra tonne of fuel on an EU voyage needs allowances for its CO₂ (and from 2026 its methane and nitrous oxide) and adds to the FuelEU deficit of a ship above the limit.
When does a hull cleaning pay back?
When its cost is covered by the daily cost of the fouling it removes. A ship with a large EU share pays back sooner, because each tonne of fuel saved also saves allowances.
EU ETS, FuelEU, CII and UK ETS for each ship, from the public register or your own data.