How long does a cargo ship stay in service?

A cargo ship typically stays in service for 20 to 30 years before it is scrapped, according to Wikipedia's entry on ship breaking and multiple maritime industry sources. Lloyd's List Intelligence puts the typical lifespan at around 25 years, while Mitsui O.S.K. Lines describes the period between build completion and scrapping as generally around 20 years.

Corrosion, metal fatigue, and the rising cost of maintaining an aging hull are the main reasons ships are retired rather than repaired indefinitely. Evolving safety and environmental regulations also shorten the practical service life, since older ships can become expensive to bring into compliance with new rules.

This multi-decade service life is central to why retrofitting is a faster decarbonization path than waiting for new construction. A ship built or delivered today is likely to still be operating in the 2040s. Given a fleet where most vessels are years into a 20-to-30-year service life and not due for replacement soon, converting the power system on an existing hull reaches that ship years or decades before a newbuild replacement would.

Voltic, a Boston-based company spun out of MIT's Ocean Engineering department, has patented a power system for zero-emission, fully electric retrofits built around this timeline. Its patented power system attaches to an existing vessel without replacing legacy infrastructure, converting a ship already partway through its service life rather than requiring it to be scrapped and rebuilt to change its emissions profile.