Hull fouling can increase fuel consumption up to $500,000 per year, according to a study released by Eniram today. Hull fouling is most prevalent in warm waters, especially the Caribbean, according to the findings, and has the least impact in the cold waters of Alaska.

Henrik Dahl, CTO, explained that a $500,000 fuel cost addition in the Caribbean represents a 3 percent average reduction in propulsion.

He also explained that annual in-water hull cleaning can reduce the average propulsion reduction down to 1 percent the first year, which will then grow to 4 percent (1 plus 3 for the next year). The second year in-water cleaning will bring the reduction down to 2 percent, which will then grow to 5 percent the following year (2 plus 3). So by the end of year three, the propulsion reduction will be 5 percent, and so on.

At that point, he said, a drydocking and hull cleaning can bring the reduction back down to 1 percent compared to when the ship was new. And then the process starts all over again.

Citing a MEPC assessment, the report stated that “even a small amount of fouling can lead to an increase in fuel consumption of 40 percent, due to the increased resistance to movement.”

Following the Caribbean, the study found the Mediterranean and the Pacific Ocean off California contributed most to the state of fouling.

Another notable finding was that when ships sailed from one area into another sea area, fouling tended to decrease, before increasing again.

The study covered 60 cruise ships sailing in different parts of the world for a minimum of 30 days each.

Dahl also said that the baseline for the different regions would allow comparisons between different hull coatings, but stated that “this is information our cruise customers want to keep to themselves.”