The maritime industry is undergoing a fundamental transformation as electric propulsion systems shift from niche applications to a mainstream solution for reducing emissions and improving operational efficiency. Driven by tightening environmental regulations, falling battery costs, and advances in power electronics, ship owners and operators are increasingly adopting fully electric and hybrid-electric powertrains. However, the safe and efficient integration of these new technologies depends on a rapidly evolving landscape of standards and regulations. This article examines the key emerging frameworks governing electric propulsion in the maritime sector, covering international and regional rules, technical standards for battery and electrical systems, and the challenges that lie ahead.

Background of Electric Propulsion in Maritime Industry

Electric propulsion in ships is not entirely new – some submarines and naval vessels have used diesel-electric systems for decades. What is new is the widespread adoption of large-scale battery banks and fully electric drives for commercial and passenger vessels. The primary drivers are the International Maritime Organization’s (IMO) initial strategy on reduction of greenhouse gas (GHG) emissions from ships, which aims to cut total GHG emissions by at least 50% from 2008 levels by 2050, and the growing pressure from ports and coastal states to reduce local air pollutants such as NOx, SOx, and particulate matter.

Electric propulsion systems offer several well-documented advantages. Beyond near-zero emissions at point of use, they provide significantly lower noise and vibration levels, which benefits both crew comfort and marine life. Electric motors have higher efficiency than internal combustion engines, particularly at partial loads, and they enable greater flexibility in vessel design by eliminating the need for long drivelines. Regenerative braking can also be used in some applications to recover energy. Currently, the majority of electric vessels are ferries, port tugs, inland cargo ships, and offshore support vessels, though the technology is starting to appear in short-sea and coastal shipping. According to a report by DNV GL, the number of battery-powered ships in operation or on order exceeded 400 by the end of 2022, and continues to grow rapidly.

Nevertheless, the maritime environment presents unique challenges for electrical systems: saltwater exposure, constant motion and vibration, extreme temperatures, and long operational lifetimes. These conditions demand specific safety and design standards that go beyond those for land-based applications. The development of comprehensive regulations and class society rules is therefore critical.

Emerging Standards for Electric Maritime Vessels

Standards for electric propulsion in shipping come from multiple sources – international bodies such as the International Electrotechnical Commission (IEC), classification societies like Lloyd’s Register, DNV GL, and Bureau Veritas, and the IMO itself. These standards cover the entire system from battery chemistry to power distribution and emergency shutdown procedures.

Battery Safety and Management

Battery safety is the single most important area of concern. Large lithium-ion battery packs store a huge amount of energy in a confined space. A thermal runaway event can release flammable gases and cause fires that are difficult to extinguish on board. Standards such as IEC 62660 (secondary lithium-ion cells for propulsive applications) and IEC 63057 (road vehicles – but often referenced) are used as the basis for type approval, but maritime usage adds durability and environmental resistance tests unique to shipboard service.

Classification societies have published extensive rules. For example, DNV GL’s class rules for battery systems (DNVGL-RU-SHIP Pt.6 Ch.2) specify requirements for battery cell and pack testing, thermal management including fire detection and suppression, ventilation, and the installation of robust Battery Management Systems (BMS). The BMS must monitor temperature, voltage, and current for each cell or module, ensure cell balancing, and automatically disconnect the battery if conditions exceed safe limits. The IMO has also issued an interim guideline (MSC.1/Circ.1625) on the use of lithium-ion batteries on ships, which addresses fire safety, charging systems, and the need for a battery management system.

Another important standard under development is IEC 62619 (secondary lithium cells for industrial applications) which covers safety testing for large batteries. Additionally, recycling and end-of-life management are increasingly considered; the EU’s Battery Regulation (2023) requires that batteries placed on the market are designed for recyclability and contain recycled content, which will affect maritime battery suppliers.

Electrical System Design

The electrical power system on an electric ship typically operates at high voltage DC (e.g., 1000 V or higher) to reduce current and cable losses. Standards such as IEC 60092 series (Electrical installations in ships) and IEC 61439 (low-voltage switchgear and controlgear assemblies) are adapted for the maritime environment. Specific requirements include:

  • Redundancy: Power generation and distribution should have at least two independent sources to allow continued operation after a single failure.
  • Insulation monitoring: High-voltage systems in ships must have continuous insulation resistance monitoring to detect faults early.
  • Waterproofing and ingress protection: Electrical enclosures must meet at least IP56 or higher to withstand spray and hose-down cleaning.
  • Arc flash protection: DC arc faults are harder to extinguish than AC arcs; standards require arc fault detection devices (AFDDs) and appropriate personal protective equipment (PPE) for crew.

IEC standards provide the technical foundation, while classification society rules add operational and certification requirements. The International Association of Classification Societies (IACS) has also developed unified requirements (URs) for electrical installations, including those for electric propulsion, to ensure consistency across member societies.

Charging Infrastructure Standards

For vessels that require shore charging, standardized connectors and protocols are essential. The CHAdeMO association has developed a megawatt charging system (MCS) for heavy vehicles, which is being considered for maritime use. Meanwhile, the IEC and ISO are working on ISO/IEC 15118-20 for high-power charging communication. Ports in Norway and the Netherlands already use a custom high-power plug, but a global standard is needed to avoid conflicting infrastructure. The IMO’s Maritime Safety Committee is expected to address this through its circulars on alternative power systems.

International and Regional Regulations

International Maritime Organization (IMO) Role

The IMO is the key international body setting safety and environmental regulations. For electric propulsion, the IMO has not yet issued a dedicated code equivalent to the IGF Code for gas-powered ships. Instead, it relies on the Safety of Life at Sea (SOLAS) convention and its amendments. In 2019, the IMO Maritime Safety Committee approved MSC.1/Circ.1625, the interim guidelines for the use of lithium-ion batteries on ships. These guidelines cover installation, operation, and fire safety, and are expected to move toward mandatory requirements within the next revision of SOLAS Chapter II-1 (construction – subdivision and stability) and Chapter II-2 (fire protection).

On the environmental side, the IMO’s Energy Efficiency Design Index (EEDI) and the new Carbon Intensity Indicator (CII) and Energy Efficiency Existing Ship Index (EEXI) create strong incentives for electric propulsion because they measure emissions per transport work. Vessels that can operate on battery power for part of their journey (e.g., in port or emission control areas) achieve a lower average carbon intensity. The IMO is also considering mid-term measures including a possible carbon levy, which would further improve the economics of electric propulsion.

Regional Regulations and Incentives

Regional and national authorities are moving faster than the IMO, often using subsidies and mandates to accelerate uptake:

  • European Union: The Fit for 55 package includes the FuelEU Maritime regulation, which requires a gradual reduction in the greenhouse gas intensity of energy used on board ships trading in EU waters (starting at 2% reduction in 2025, up to 80% by 2050). Shore-side electricity supply for passenger and container ships at major EU ports will become mandatory by 2030 under the Alternative Fuels Infrastructure Regulation (AFIR). The EU also funds projects such as ELEKTRA (electric ferry) and HYSEAS II (hydrogen-electric vessel).
  • Norway: A world leader in electric ferries, Norway has subsidized hundreds of battery-ferry conversions and requires all new ferries on public tenders to be zero-emission or hybrid. The country’s NOx fund also provides financial support for battery installations.
  • China: The Chinese government has published the Green Shipping Development Plan, which promotes battery electric and hybrid vessels for inland waterways and coastal routes. Several large all-electric container ships are already operating on the Yangtze River.
  • United States: The Environmental Protection Agency (EPA) and California Air Resources Board (CARB) have set aggressive emissions targets for harbor craft and ferries. The US Coast Guard is updating its regulations for electric propulsion systems, based on a policy letter from 2021 that requires compliance with recognized standards such as ABS rules and IEC guidelines.

Regional incentives often include capital subsidies for the difference between a conventional and an electric propulsion system, as well as operational benefits such as reduced port fees for green vessels. This patchwork of regulations creates both opportunities and complexity for global operators.

Challenges and Future Outlook

Technical and Economic Challenges

Despite rapid progress, several obstacles limit large-scale deployment:

  • Battery cost and weight: Although lithium-ion cell prices have dropped by nearly 90% over the past decade, they remain a significant portion of the vessel cost. For deep-sea vessels, the weight and space required for batteries to achieve transoceanic range are prohibitive with current technology. This limits electric propulsion mainly to short-sea, ferry, and inland operations.
  • Port infrastructure: High-power shore charging requires grid upgrades and large investments. Few ports currently have megawatt-level charging capacity. International standards for connectors and communication are not yet fully harmonized, leading to uncertainty for port planners.
  • Safety certification: The novelty of large battery systems means that classification societies and flag states are still building experience. Approval processes can be lengthy, and every new design may face a first-of-a-kind certification challenge.
  • Crew training: Handling high-voltage batteries and electrical fire emergencies requires specialized training, which the global seafarer population generally lacks. The STCW convention (Standards of Training, Certification and Watchkeeping) does not yet include mandatory modules for electric propulsion.
  • Lifecycle and end-of-life: Battery recycling infrastructure for maritime size packs is underdeveloped. By 2030, thousands of retired ship batteries will need disposal or second-life applications, requiring new regulations and supply chains.

Future Outlook

The trajectory is clear: electric propulsion will become the standard for vessels operating on fixed routes with predictable power demand. Advances in solid-state batteries could dramatically increase energy density and safety, opening up longer routes. Hydrogen fuel cells may compete with batteries for larger ships where charging is impractical, but electric hybrids (fuel cell + battery) are also being developed. The EU and Japan are already funding hydrogen-electric ship projects.

The IMO is expected to introduce mandatory requirements for battery safety in the next revision of SOLAS, likely by 2026. Meanwhile, classification societies are refining their rules and publishing unified interpretations. The Maritime Battery Forum (MBF) and the Global Maritime Forum are driving collaboration between industry, regulators, and researchers to address knowledge gaps.

In conclusion, the emerging standards and regulations for electric propulsion are creating a robust framework for safe, sustainable, and efficient maritime transportation. While challenges remain in cost, infrastructure, and certification, the combined push from international bodies, regional regulators, and the private sector is accelerating the transition. For ship owners and operators, staying ahead of these evolving rules is not just a compliance issue – it is a strategic opportunity to gain competitive advantage in the green shipping era.