Updated 24 november 2025.
The push toward greener vessel operations continues to accelerate. With rising fuel prices, tightening emission regulations and growing pressure to reduce lifecycle costs, vessel owners are rethinking their propulsion choices. Efficient propulsion technology plays a critical role in reducing both energy consumption and environmental impact, and the right system can dramatically improve operational performance.
Consider this: If your propulsion system reduces energy consumption by 30%, you gain a 30% reduction in energy cost, and a 30% reduction in emissions. Efficiency and sustainability are inseparable.
This article explores the main energy sources used in marine propulsion, what makes a propulsion system truly efficient, and why certain solutions, particularly Controllable Pitch Propeller (CPP) technologies, are emerging as strong candidates for a greener future.
Most vessels today still rely on diesel engines, a proven but emission-intensive power source. In many cases, diesel engines operate outside their optimal load window, often achieving below 50% efficiency, which results in unnecessary fuel burn.
While fossil-fuel propulsion varies, from a simple direct diesel–shaft setup to more advanced diesel-electric configurations, the broader industry trend is shifting toward systems that support lower emissions, lower operating costs and greater flexibility.
1. Hybrid propulsion systems
2. Fully electric propulsion
3. Emerging fuels
Examples include hydrogen, methanol, ammonia or biofuels. These fuel types require propulsion systems capable of managing:
Regardless of energy source, propulsion efficiency remains critical. An efficient propulsion line reduces the total power demand, making low-emission energy sources more viable.
Suggested reading: The most valuable energy is the one you do not use
Choosing a propulsion system is not just about the engine or motor. The entire propulsion line matters:
The following factors determine real-world efficiency:
A well-optimized hull reduces required power. Common mistakes include:
A larger diameter allows lower rotational speed, which increases:
For high-speed vessels, weight reduction becomes particularly important to maintain low resistance and high efficiency.
Efficiency depends on how well the components work together:
A poorly integrated system can eliminate the advantages of even the most efficient components.
Read more: What is Important When Selecting Propulsion Technology
A Controllable Pitch Propeller (CPP) system is often the most efficient and adaptable solution across varying speed ranges and operational profiles.
Reduced energy consumption (OPEX savings): Lower required energy makes low- or zero-emission solutions more feasible.
Smaller batteries in hybrid/electric vessels: Because the propulsion line is more efficient, total installed energy can be lower, reducing weight, cost and charging needs.
Highly adaptable to future fuels: CPP integrates more easily with battery-electric systems, hydrogen fuel cells, methanol and e-fuels, hybrid configurations
Superior manoeuvring and thrust capacity: CPP systems produce strong bollard push, making them ideal for offshore wind vessels, aquaculture vessels and harbour craft.
Even the greenest onboard technology cannot deliver full environmental benefit if the shoreside energy is not renewable. Charging systems must be supported by:
Read more: Potential Fuel Saving in Converting From Water Jet to CPP
When selecting a propulsion system, economics and environmental performance are deeply connected. A system that is truly efficient reduces both operational cost and emissions.
While battery-based propulsion is environmentally attractive, it increases vessel weight — which in turn raises energy demand. The key is balancing propulsion efficiency with energy storage capacity.
For many vessel types, a CPP system integrated into a well-designed propulsion line stands out as the optimal long-term solution. It offers:
However, incentives and infrastructure must support the transition. For zero-emission vessels to succeed commercially, it must be cheaper to operate green.