Benchmarking energy efficiency and regulatory compliance of ferries: a fleet-scale EEXI and EEDI assessment

The maritime industry is under increasing pressure to improve energy efficiency and reduce greenhouse gas emissions. This challenge is particularly significant for ferries, which operate close to ports and densely populated coastal areas. The International Maritime Organization (IMO) has introduced the Energy Efficiency Design Index (EEDI) and the Energy Efficiency Existing Ship Index (EEXI) as key technical measures for improving the energy performance of new and existing ships. This paper presents a comprehensive assessment of the energy efficiency of a fleet of 776 ferries, representing one of the largest datasets analysed for this type. The attained energy efficiency indices were calculated and compared with the applicable requirements to evaluate the current level of compliance and design energy efficiency. The results show that 57.78 % of ships delivered before 2013 comply with the required EEXI, while 57.93 % of ships delivered from 2013 onwards comply with the applicable EEDI requirements and 66.21 % satisfy the corresponding EEXI requirements. The potential of two operational measures, hull cleaning and slow steaming, was investigated for ferries that failed to satisfy the requirements. Following hull cleaning of a biofilm-fouled hull, the EEXI compliance rate of ships delivered before 2020 increases from 56 % under the baseline condition to 58 %, 63 %, and 65 % when reference speed is assumed to increase by 1 %, 3.5 %, and 5 %, respectively. The results indicate that a significant proportion of the analysed fleet does not comply with the current regulations. Compliance is generally higher for larger ferries, whereas smaller ships require greater engine power limitation to achieve the compliance. The study provides a systematic benchmark of ferry energy efficiency and quantifies the effectiveness of practical operational measures for improving regulatory compliance.