Applying the EEDI / EEXI to the Superyacht Sector: Why Globally Recognised Methodologies Matter

EEDI / EEXI: Decarbonisation via a Ratings System

As outlined above, the EEDI and EEXI utilise a technical formula to measure a vessel’s CO2 emissions per transport work and employ a ratings system to determine whether each vessel is meeting its required CO2 performance.

While the detailed formula may seem complicated, the concept is surprisingly simple. Furthermore, it’s proving to be user-friendly and effective in real-world applications. By using established benchmarks, realistic reduction rates and straightforward ratings, the IMO ensures the EEDI and EEXI are effective in reducing CO2 emissions – which is why we based our own SEA Index methodology on the same principles, adapting them to the typical operational profile of superyachts.

Can the EEDI and EEXI Regulations Apply to Yachts?

Yes – we’re already doing it! We’ve developed the SEA Index based on the IMO’s EEDI and EEXI regulations and adapted them in accordance with a nominal superyacht operational profile.

Unlike other yachting sustainability frameworks and ratings systems, we ensure that yacht owners and stakeholders have access to scientifically-proven, internationally-recognised and third-party verified methodologies to measure and reduce CO2 emissions.  

What’s more – basing the SEA Index on the EEDI and EEXI ensures that yacht owners can access accurate emissions data via methodologies that are most likely to be applied if the IMO extends its regulations to the yachting sector. 

Will the IMO Regulate the Yachting Sector?

Although the IMO has not yet applied its regulatory framework to the yachting sector, many industry stakeholders expect this to change in the mid- to long-term. Emitting approx. 5 million tonnes of CO2 per year, the yachting sector is likely to face increasing environmental regulation if voluntary emissions reductions and self-regulation is ineffective. 

This means that yacht owners, manufacturers and architects have a limited amount of time to reduce emissions and increase sustainability if the sector is to avoid international regulation.

Fortunately, there are numerous ways to reduce CO2 emissions and enjoy more eco-responsible yachting without negatively impacting your experience at sea. From on-board sustainable tech designed to cut carbon emissions to enhanced hull design, to route optimisation, yacht owners can incorporate cutting-edge solutions to maximise sustainability. 

However, having access to accurate and impartial emissions data is critical to monitoring and reducing CO2 throughout the yachting sector – and that’s where SEA Index comes in. 

Using the retrofit recommendations issued alongside every SEA Index certification, we even make it possible to enhance the sustainability of your vessel in accordance with our EEDI- and EEXI-based methodologies.

While the jury’s still out on whether the IMO will expand their reach to the yachting sector, yacht owners and other stakeholders can be proactive in reducing emissions in order to retain the freedoms and independence we enjoy and use proven, independent frameworks to monitor and reduce the environmental impact of yachting. 

How Does SEA Index Measure CO2 Emissions?

In a bid to empower owners and increase transparency throughout the yachting sector, we have developed an impartial and unbiased Index that measures and rates the CO2 intensity of yachts over 25 metres.

To ensure that the SEA Index is scientifically sound, we’ve emulated the principles of the IMO’s EEDI and EEXI and adapted them to superyachts by incorporating a fixed typical operational profile (time at sea, at anchor, berth and manoeuvring). 

Our methodology assesses the energy intensity of a vessel based on the amount of CO2 it emits per gross ton per hour, taking into account but not limited to, the rated installed power of the engines, generators, electrical load balance and specific fuel consumption data. 

By using ‘CO2 per gross ton per hour to determine a vessel’s carbon intensity, we ensure that yachts can be compared based on their environmental impact. This facilitates the unbiased comparison of varying yachts and enables owners and yachting stakeholders to make informed decisions regarding purchases, retrofits, insurance, charters and more.

The Science Behind SEA Index Ratings

In the same way that the EEDI and EEXI use ratings systems to reflect a vessel’s carbon intensity, the SEA Index assigns each certified yacht a rating, based on the amount of CO2 it emits per gross ton per hour, based on its design.

To develop our ratings system and ensure it provides a reliable benchmark, we’ve analysed data from over 800 yachts and applied a fixed superyacht operational profile (at sea, anchor, berth and manoeuvring).

Using this data, we were able to establish the minimum and maximum CO2 thresholds for each of our five ratings:

As shown in the graph above, the SEA Index ratings system runs from 1 to 5 stars, with 5 star vessels being the most energy efficient.

Our reference line, or baseline, sits at the midway point and superyachts that achieve this level of energy efficiency are awarded 3 stars to reflect their average environmental performance. Yachts that are 25% or 50% more efficient than this baseline are awarded 4 or 5 stars, respectively.

Future-proofing the Global Superyacht Fleet

Like the IMO, we recognise that the maritime landscape is continually evolving and we endeavour to update the SEA Index to reflect changes in the yachting sector. As more sustainable on-board technology becomes available, for example, we ensure it is included in our assessment methodology to ensure the vessel’s true CO2 emissions are accurately measured.

In 2024, we became the first yachting association to offer non-biased CO2 certification incorporating methanol and fuel-cell technology. This most ambitious development to date is now available to all SEA Index applicants.

As well as continually reviewing and updating our tools to reflect the evolving landscape, we ensure that every SEA Index certificate comes with a range of recommendations to help owners explore the right improvement options for their yacht. 

At SEA Index, we pride ourselves on applying the same rigorous assessment to every yacht that undergoes our certification process. Combining a data-driven, transparent and unbiased methodology with third-party verification from maritime Class Society, Lloyd’s Register, our superyacht CO2 rating system is fast-becoming the sector’s most trusted environmental benchmark.

To find out more, get in touch with our team and start the SEA Index certification process now!