Ship Energy Efficiency: Here Is All You Need to Know

If you ask ten ship owners what “energy efficiency” really means, you’ll probably get ten different answers. Some will talk about fuel savings. Others will mention compliance with the IMO’s EEXI regulations. But energy efficiency isn’t just a regulatory checkbox, it’s a performance philosophy shaping how modern ships are designed, operated, and even valued.

Let’s unpack what energy efficiency means in shipping, why it matters, and how the industry measures and improves it through standards like EEDI and EEXI.

1. Why Energy Efficiency in Shipping Matters

Shipping moves around 80% of global trade by volume, but it also contributes nearly 3% of global CO₂ emissions each year [1]. With stricter emission targets under the International Maritime Organization’s (IMO) greenhouse gas strategy, efficiency has become both an environmental and economic priority.

Fuel is the single largest operating cost for most ships, often 50–60% of total voyage expenses [2]. Improving efficiency by even 5–10% can save millions annually for large fleets while cutting emissions dramatically.

In simple terms: better efficiency means lower costs, cleaner oceans, and stronger returns on assets.

2. The Basics: What Is Ship Energy Efficiency?

The energy efficiency of ships refers to how effectively a ship converts fuel energy into useful propulsion and transport work. It’s the balance between the energy consumed and the amount of cargo moved over a certain distance.

Here’s the ship energy efficiency formula often used in regulatory frameworks:

Energy Efficiency=Fuel Energy Input (MJ)Transport Work (tonnes × nautical miles)\text{Energy Efficiency} = \frac{\text{Fuel Energy Input (MJ)}}{\text{Transport Work (tonnes × nautical miles)}}Energy Efficiency=Transport Work (tonnes × nautical miles)Fuel Energy Input (MJ)​

The lower this ratio, the more energy-efficient the ship.

This formula forms the basis of the IMO’s two cornerstone measures for ship efficiency: the Energy Efficiency Design Index (EEDI) and the Energy Efficiency Existing Ship Index (EEXI).

3. Understanding EEDI and EEXI: The Core Standards

Both EEDI and EEXI are tools for measuring how energy-efficient ships are, but they apply to different ship generations.

EEDI (Energy Efficiency Design Index) applies to newly built ships. Introduced by the IMO in 2013, it measures the theoretical CO₂ emissions per ton-mile based on the ship’s design efficiency [3]. It sets progressively stricter benchmarks every five years, pushing shipbuilders to design ships that consume less fuel and emit less CO₂.

EEXI (Energy Efficiency Existing Ship Index) applies to ships already in service. Launched in 2023, EEXI ensures that older ships also meet similar energy efficiency standards through technical modifications and operational changes [4].

Here’s a quick table showing the EEDI and EEXI difference:

Aspect	EEDI	EEXI
Applies To	New ships (built after 2013)	Existing ships (pre-2013 builds)
Focus	Design efficiency	Operational performance
Measurement Basis	CO₂ emissions per ton-mile	Adjusted CO₂ emissions per ton-mile
Key Methods to Improve	Hull design, propulsion systems	Engine power limitation, retrofits, route optimization

In essence, EEDI is about how ships are built, while EEXI is about how ships perform.

4. Ship Energy Efficiency Examples: Real-World Improvements

Energy efficiency doesn’t happen in one big step, it’s the sum of hundreds of small optimizations.

Here are some ship energy efficiency examples already reshaping the industry:

1. Hull Optimization: Modern hull coatings reduce drag by up to 10%, saving thousands of tons of fuel per year [5].

2. Waste Heat Recovery: Ships now capture exhaust heat to generate electricity, improving total efficiency by up to 8% [6].

3. Air Lubrication Systems: Microbubble layers under the hull reduce friction between ship and water, cutting fuel use by 3–9% [7].

4. Propeller Upgrades: Advanced propeller blades and ducts can increase propulsion efficiency by 4–6% [8].

5. Speed Optimization: A slower, optimized cruising speed, known as slow steaming, can lower fuel consumption by 15–30%, though it increases voyage time [9].

Each of these improvements makes ships not only greener but also more profitable to operate.

5. How EEXI Compliance Works

For ship owners, achieving EEXI compliance isn’t optional, it’s mandatory under IMO’s MARPOL Annex VI. Ships must calculate their EEXI value using the formula:

EEXI=CO2 EmissionsTransport Work (tonnes × nautical miles)EEXI = \frac{CO₂ \text{ Emissions}}{\text{Transport Work (tonnes × nautical miles)}}EEXI=Transport Work (tonnes × nautical miles)CO2​ Emissions​

The required EEXI varies by ship type and size. To comply, owners often adopt one or more of these methods:

• Engine Power Limitation (EPL): Reduces the ship’s maximum engine output to cap emissions.

• Shaft Power Limitation (SHaPoLi): Controls power through the propulsion shaft rather than the engine.

• Retrofits and Upgrades: Replacing propellers, installing energy-saving devices, or improving automation systems.

• Operational Adjustments: Using weather routing software or trim optimization to enhance performance.

By January 2025, more than 70% of the global fleet had either implemented EPL or filed their EEXI compliance documents [10].

6. Beyond EEXI: Continuous Efficiency in Operation

Once a ship meets design or retrofitted efficiency standards, the next step is maintaining it through Energy Efficient Ship Operation (EESO).

EESO focuses on real-world behavior, how the ship is actually sailed, loaded, and maintained. Some best practices include:

• Voyage Planning: Adjusting routes based on real-time weather and current data to minimize distance.

• Ballast Optimization: Keeping the right ballast-water balance to reduce drag and improve stability.

• Regular Maintenance: Clean hulls and propellers can save up to 10% in fuel compared to fouled surfaces [11].

• Digital Monitoring: Advanced sensors and Big Data analytics track performance and identify inefficiencies automatically.

Together, these steps maintain compliance and maximize profitability.

7. Why Energy Efficiency Matters for Ship Owners

For ship owners and stakeholders, efficiency isn’t just about sustainability, it’s about value.

Energy-efficient ships command higher charter rates, maintain stronger resale value, and qualify for green financing incentives from institutions aligned with the Poseidon Principles [12].

Under the EU Emissions Trading System (ETS), inefficient ships could face additional carbon costs. As carbon prices climb toward €100 per ton of CO₂, efficiency becomes a financial advantage rather than a burden [13].

Efficient ships also position themselves better for future regulations, including the IMO’s 2030 and 2050 emission reduction targets.

8. The Future of Energy Efficiency in Shipping

The next decade will push ship efficiency even further through new technologies and digital integration:

• AI-Powered Routing: Predictive algorithms adjust speed and routes in real-time.

• Hybrid and Electric Propulsion: Battery-assisted systems reduce fuel burn on short routes.

• Alternative Fuels: Ammonia, hydrogen, and methanol are emerging as scalable, low-carbon solutions.

• Blockchain & Data Integration: Real-time energy tracking enhances transparency for regulators and shipowners alike.

According to the International Chamber of Shipping, global investments in green shipping technologies could exceed $1 trillion by 2050 [14].

The takeaway? Energy efficiency isn’t a passing compliance requirement, it’s the foundation for the shipping industry’s next growth phase.

9. Conclusion

Energy efficiency in shipping isn’t just about equations or regulations. It’s about rethinking how ships operate, from design to daily voyage.

The combination of EEDI and EEXI ensures that both new and existing ships move toward lower emissions, better fuel economy, and long-term sustainability. For ship owners, energy efficiency delivers measurable benefits: lower costs, higher asset value, and compliance peace of mind.

At Shipfinex, we see efficiency not as a limit, but as an opportunity, a chance to build ships that are smarter, greener, and more valuable in a tokenized future of maritime ownership.

Disclaimer:

This material is provided for informational purposes only and does not constitute financial, investment, or legal advice. All digital assets carry inherent risks, including potential loss of capital. Past performance is not indicative of future results. Please review the relevant offer and risk disclosures carefully before making any financial decision.

References (APA 7th Edition)

1. International Maritime Organization. (2023). Fourth IMO GHG Study 2020 Summary. Retrieved from https://www.imo.org/en/OurWork/Environment/Pages/Fourth-IMO-GHG-Study-2020.aspx

2. UNCTAD. (2023). Review of Maritime Transport 2023. Retrieved from https://unctad.org/webflyer/review-maritime-transport-2023

3. IMO. (2024). Energy Efficiency Design Index (EEDI). Retrieved from https://www.imo.org/en/OurWork/Environment/Pages/Technical-and-Operational-Measures.aspx

4. DNV. (2023). EEXI Implementation and Compliance. Retrieved from https://www.dnv.com/maritime/insights/topics/eexi.html

5. Wärtsilä. (2024). Hull Coating Efficiency Study. Retrieved from https://www.wartsila.com/insights/article/hull-coatings-efficiency

6. MAN Energy Solutions. (2024). Waste Heat Recovery Systems in Marine Engines. Retrieved from https://www.man-es.com/

7. Silverstream Technologies. (2023). Air Lubrication Technology Overview. Retrieved from https://www.silverstream-tech.com/

8. Wärtsilä. (2023). Propeller Efficiency and Design Innovations. Retrieved from https://www.wartsila.com/marine/products/propulsion

9. Clarkson Research. (2024). Operational Efficiency Report. Retrieved from https://www.clarksons.net/

10. DNV GL. (2025). Maritime Forecast Report. Retrieved from https://www.dnv.com/maritime/

11. Lloyd’s Register. (2024). Hull Cleaning and Maintenance Best Practices. Retrieved from https://www.lr.org/en/insights/

12. Poseidon Principles. (2024). Green Financing for Maritime Assets. Retrieved from https://www.poseidonprinciples.org/

13. European Commission. (2024). EU Emissions Trading System: Maritime Extension. Retrieved from https://climate.ec.europa.eu/eu-action/eu-emissions-trading-system-eu-ets_en

14. International Chamber of Shipping. (2024). Maritime Technology Investment Outlook. Retrieved from https://www.ics-shipping.org/