An electric avenue to greener ships

For years, the idea of large, fully electric ships felt like a distant ambition.  

Today, that future is within reach. Battery technology has matured, costs have fallen and new regulations are reshaping the economics of shipping.  

For RoPax vessels, especially cargo-focused designs, the case for going fully electric is stronger than ever. Oskar Levander, Kongsberg Maritime’s VP Business Development – Emerging Solutions, explains the potential decarbonising of major transport routes. 

Kongsberg Maritime carried out an extensive study, looking at a variety of European ferry routes, from the Mediterranean to the Gulf of Finland. Oskar says: “We analysed total costs for diesel versus battery-electric RoPax vessels over the period between 2030 and 2040.  

“The results were clear: electric RoPax ships can deliver 8 to 15 per cent lower lifetime costs despite higher upfront investment,” Oskar notes. 

“Additionally, operational expenditure [OpEx] savings range from 20 to 27 per cent, thanks to lower energy costs and zero ETS exposure. We looked at a lot of routes, but some of the most potential routes are across the Gulf of Finland and the English Channel.” 

These busy routes are favourable because of the short distances and frequent sailings making them ideal for electrification. 

Just two years ago, diesel RoPax vessels were clearly cheaper than their electric counterparts. That’s no longer true. Battery prices have fallen sharply, and ETS costs for fossil-fuel ships are significant, adding millions of euros annually to the costs of operating on busy routes such as Tallinn to Helsinki or Dover to Calais.  

“FuelEU adds further penalties for conventional fuels, while electric vessels with zero emissions can earn extra revenue by pooling with other vessels,” says Oskar. “Battery-electric RoPax vessels can cut operating costs and generate extra income and thereby reduce total annual costs by millions of Euros.” 

Kongsberg Maritime has developed two vessel designs: one for cargo and one for passengers. The cargo RoPax design optimises speed and schedule.  

Oskar says: “Looking at the Vuosaari [Finland] to Muuga [Estonia] route, that means operating at slower speeds, around 16 knots, and having four crossings per day instead of six. This reduces energy demand and cargo throughput is kept unchanged by increasing lane metres for trucks and trailers. Propulsion comes from two Kongsberg Maritime Elegance electric pods for high efficiency and manoeuvrability.”  

Battery capacity ranges from 35–56 MWh, with modular compartments along the hull sides for easy expansion. The simplified layout uses straight walls and fewer watertight doors, reducing complexity and building cost. 

“We’ve integrated intelligent energy management, modular battery rooms and heat pump systems to replace waste heat from engines,” he says. “It’s practical, efficient and future-ready.” 

The passenger-focused concept targets higher speeds of up to 20 knots and combines a centre shaft line and controllable pitch propeller (CPP) with two pods for added power to suit the higher speed operation. It features extensive public spaces, tax-free retail and cabins arranged for comfort, making it ideal for routes such as Tallinn to Helsinki where passenger demand is high. Battery capacity can reach 100 MWh, supported by advanced energy management systems. 

“Passenger RoPax vessels pose unique challenges,” Oskar explains. “They require more power and faster charging, but the principles of electrification remain the same: efficiency, sustainability and customer appeal.” 

Electrification isn’t without hurdles. “The biggest is the charging infrastructure. High-power connections aren’t available everywhere and ports must invest. 

“Collaboration between shipowners, ports, grid operators and even cargo owners is essential. So, this is a systems and operational challenge, not just a shipdesign challenge. 

“For RoPax operators, the question isn’t if electrification will happen, it’s when,” he concludes. “From where I stand, that time is now.”