Efficiency First: Wärtsilä’s Case for Smarter Propulsion

Bernd Bertram, Vice President, Propulsion at Wärtsilä, on Gate Rudder’s fuel savings, hybrid propulsion and why integrated vessel design will define the next five years

1. Wärtsilä has posted an all-time-high order intake with record marine orders. How much of that surge is propulsion-specific, and what’s driving it: newbuild fleet renewal, retrofits, or both?

The marine industry is going through a significant period of transition and we’re seeing growing interest in propulsion as part of a broader efficiency and decarbonisation strategy. The conversation has moved beyond simply replacing equipment. Owners are increasingly asking how they can improve the efficiency of the entire vessel and reduce energy demand while maintaining flexibility for the future.

Efficiency is no longer a nice-to-have. Rising fuel costs, tightening regulations and uncertainty around future fuel pathways are exactly the reasons shipowners are looking for solutions that deliver immediate operational benefits while keeping long-term flexibility on the fuel question.

Geopolitical disruption plays a role as well. Rerouting and longer voyage distances are supporting vessel utilisation, which in turn reinforces the case for propulsion efficiency for fleets.

There is a strong role for both newbuilds and retrofits to play. On the newbuild side, meeting increasingly stringent Energy Efficiency Design Index (EEDI) baselines often requires measures such as de-rating main engine power or adopting approved energy saving devices. Gate Rudder would help shipowners to achieve their target EEDI rating. Newbuild projects create opportunities to optimise the whole vessel from day one, while the existing fleet represents a significant opportunity to improve efficiency, reduce fuel consumption and lower emissions through upgrades and optimisation.

For retrofits, owners are protecting their vessels’ commercial position as much as their compliance status. For example, with the tightening of IMO’s Carbon Intensity Indicator, CII requirements are being included in charter contracts, which means a D- or E-rated vessel can be excluded from cargo programmes altogether. Retrofits or upgrades give owners a way to protect a vessel’s rating and marketability now, without needing to commit to a specific fuel pathway – this is the kind of flexibility shipowners are looking for.

• At your stand you’re demonstrating the Gate Rudder™ simulator alongside CPP controls. What’s the real-world efficiency delta owners are seeing from Gate Rudder versus conventional rudder-propeller setups, and what vessel segments suit it best?

What has been particularly encouraging is that across full-scale applications we have seen a consistent trend of up to 20% fuel savings with Gate Rudder compared with representative conventional rudder arrangements.

The concept is built around a relatively simple idea. Traditionally, the rudder has been viewed as a steering device. We see it as part of the overall propulsion system. Every time a vessel makes a course correction there are hydrodynamic losses associated with the interaction between the propeller and rudder. Gate Rudder is designed to reduce those losses while improving manoeuvrability.

The distinction matters because vessels do not spend their lives sailing in a perfectly straight line. They are constantly making small course corrections, and those operational realities need to be factored into any assessment of propulsion efficiency. We have carried out full-scale CFD studies on Japanese sister vessels – one fitted with a conventional flap rudder and one with Gate Rudder. Even at the relatively small steering angles associated with normal seakeeping, we see significant differences in hydrodynamic behaviour. Beyond straight-line efficiency, we also see advantages in manoeuvrability, course keeping and maintaining speed during turns.

Gate Rudder is particularly attractive for single-screw merchant vessels where efficiency is a key priority and where propulsion, steering and hull design can be optimised together. It can technically be fitted to existing vessels, though the full performance and economic benefits are realised when it is built into the vessel design from the outset since it relies on the hull form, propulsion layout, and steering system being optimised together.

• Hybrid and full-electric propulsion keep expanding beyond ferries and short-sea into deep-sea segments. Where is Wärtsilä seeing the real commercial tipping point for electrification on larger tonnage?

I don’t think there is a single tipping point because the economics depend heavily on vessel type, route, operating profile and access to charging infrastructure.

Sometimes the industry talks about electrification as a destination. In reality, it’s a tool. The real question is not whether a vessel should be electric, but which combination of technologies delivers the best economic and operational outcome.

We already see strong opportunities for hybridisation. Wärtsilä will be supplying a hybrid propulsion package for Vertom Group’s four 10,700 DWT geared tween decker vessels. The package is designed to optimise vessel propulsion efficiency while enabling sailing modes on batteries without using combustion power. Similarly, Wärtsilä has also supplied a hybrid electric propulsion system for Canada Steam Ship Lines Group’s 11,000 DWT limestone carrier MV Yampu – the world’s first battery-hybrid self-unloading bulk carrier.

Batteries can help optimise engine loading, support peak demand and improve overall efficiency. Full electrification – whilst ideal for short-sea routes and ferries – can be more challenging as vessel size, range and energy requirements increase.

Looking ahead, I expect batteries, alternative fuels and highly efficient propulsion systems to work together rather than compete. The objective is to create the most efficient solution for the way a vessel actually operates.

• On fuel flexibility (methanol, ammonia, LNG dual-fuel) how is the propulsion side of the business, versus engines, adapting shaft lines, gearboxes and controls to accommodate multi-fuel operational profiles?

From the propulsion side, the bigger issue is flexibility rather than any individual fuel. Whether a vessel runs on methanol, ammonia or LNG dual-fuel, the propulsion system needs to evolve alongside the changing fuel landscape.

Shipowners are making decisions today about assets that will operate for decades, while the future fuel mix remains uncertain – evident in the vessel orderbook itself. According to DNV, LNG propulsion accounted for the largest share of orders, with 188 contracts representing 68% of total alternative-fuelled newbuild orders in 2025 and 31% of overall gross tonnage. Methanol-fuelled newbuild secured 6% share by tonnage with ammonia maintaining a niche presence.  The IMO’s own vote on its Net-Zero framework – meant to chart a path to its 2050 net-zero target – was adjourned to October 2026, adding regulatory uncertainty in addition to the market’s own indecision. This combination is why adaptability matters more than betting on any single fuel.

Despite whatever fuel ultimately gains market share, efficiency remains the constant. Every percentage point of efficiency reduces fuel consumption, operating costs and environmental impact. It also reduces the amount of fuel infrastructure the industry ultimately requires.

That’s why we increasingly focus on optimising the complete propulsion system, including the interaction between the propeller, rudder, controls, engine and hull, rather than looking at individual components in isolation. The greatest risk may not be choosing the wrong fuel pathway, but delaying efficiency improvements that can deliver value under almost every future scenario.

The objective is to improve performance today while maintaining the flexibility to adapt as fuel markets, infrastructure and regulations continue to evolve.

• Wärtsilä has flagged lifecycle optimisation as a top 2026 trend. What does that mean concretely for propulsion customers: performance-based service contracts, digital twins, predictive maintenance?

Lifecycle optimisation means looking beyond the point at which equipment is delivered. A propulsion system creates value over decades, not on the day it is installed.

Performance-based service contracts shift the commercial relationship from a one-off sale to an ongoing partnership anchored in mutually-beneficial outcomes. In January this year, we signed a 10-year Lifecycle Agreement with MOL Global Ship Management covering the engine and propulsion equipment on a new LNG-fuelled vessel – including Dynamic Maintenance Planning, 24/7 remote operational support and extended service intervals. Our aim here is to support the long-term reliability and reduced operating costs of the vessel rather than on a transactional parts-replacement model.

Digital twins let us model how a specific vessel or fleet behaves in reality, and use that knowledge to prioritise where investment would have the most impact. For instance, Wärtsilä built a digital twin of Carnival Corporation’s cruise ship Regal Princess using three years of operational, itinerary, and sensor data to simulate energy-saving technologies and guide fleet-wide retrofitting priorities.

Predictive maintenance tools, like Wärtsilä Expert Insight and Dynamic Maintenance Planning, use operational data to spot issues and optimise performance before they become costly problems, rather than waiting for scheduled intervals or failures. That starts with collecting operational data and using those insights to optimise maintenance, performance and fuel consumption.

It also reinforces the importance of designing the vessel as an integrated system. Small gains across the hull, propeller, rudder and control systems can translate into significant long-term operational benefits.

The industry has traditionally focused on optimising individual components. Increasingly, the opportunity lies in optimising performance throughout the lifecycle of the entire vessel.

• Retrofit versus newbuild: where is Wärtsilä seeing more propulsion-related demand right now, and does that balance shift as the existing fleet ages toward 2030 emissions milestones?

We need both, but newbuild is where we are seeing greater demand right now. Newbuild activity has increased significantly – Wärtsilä recorded 549 vessel orders in Q1 2026, up from 235 in the same period last year. Newbuild projects provide the greatest opportunity to optimise the vessel from the outset. Designers can consider the hull, propulsion, steering and energy systems together to maximise efficiency.

At the same time, the existing fleet represents one of the biggest opportunities available to tine industry today. These vessels will remain in operation for many years, and improving their efficiency can deliver immediate reductions in fuel consumption and emissions. In many cases, improving the efficiency of vessels already in operation can deliver immediate reductions in fuel consumption and emissions while extending their useful commercial life – global shipyard capacity can only renew roughly 2% to 3% of the global fleet each year (between 1,500 to 2,100 vessels per year across all sectors).

On whether the balance shifts towards 2030 – it is likely to, and mainly for regulatory reasons. As the industry awaits the IMO’s vote on its Net-Zero framework, there is growing room for a fragmented landscape of regional carbon pricing mechanisms. That fragmentation, together with tightening compliance milestones, means owners will keep evaluating both retrofit and newbuild investment. The right choice depends on the age, operating profile and long-term strategy of each vessel.

• If you had to bet on which propulsion technology will be the “must-have” standard five years from now — batteries, wind-assist, alternative fuel engines, or something less talked-about — where would you put your money?

I wouldn’t bet on a single technology. The global fleet is simply too diverse for there to be one universal answer – different vessel types, operating profiles and trade routes will require different solutions.

If I had to put money on a trend, it would be integration. The most successful vessels five years from now would not be defined by any one technology, but how intelligently they combine batteries, wind-assisted propulsion, alternative fuels, digital optimisation and propulsion design.

None of this works in isolation. Owners will need to maximise transport work from every unit of energy while retaining the ability to adapt as regulations and fuel pathways evolve. That is where I see the industry heading.

• What’s the one misconception shipowners still have about propulsion decarbonisation that you’d like to correct on record?

Perhaps the biggest misconception is that decarbonisation is primarily a question of choosing the right fuel.

Fuel is of course a vital part of the solution, but it is only one part. Before we think about what energy source powers the vessel, we should ask how efficiently that energy is being used.

Improving efficiency reduces fuel consumption, operating costs and emissions regardless of which fuel is chosen. It also helps owners manage the financial impact of sustainable fuels, many of which are already significantly more expensive than today’s conventional fuels, and in limited supply. Bio-methanol, for example, averaged around USD 2,500 per tonne MGOe in 2025 – roughly three times the cost of marine gas oil – while global production stands at only 2.2 million tonnes, falling short of potential demand that could reach 60 million tonnes by 2040.

That means looking at the vessel as a complete system, including the engine, hull, propeller, rudder, controls and operational practices.

The key question isn’t simply what fuel a vessel uses. It’s how efficiently that vessel uses energy.