It is still cheaper to build and operate a fleet of diesel-fuelled harbour tugs to manoeuvre and dock ships than to invest in battery-electric vessels, despite prices of energy storage systems (ESS’s) falling and owners benefitting from long-term lower operational expenditure and maintenance.

It is also difficult to move electric tugs between ports due to the lack of charging infrastructure.

So, the balance seems to be tipping away from green tugs in favour of the polluting diesel variety.