When a vessel at berth shuts down its auxiliary engines and connects to the port’s electrical grid, it eliminates a significant source of local air and noise pollution at a stroke. Onshore Power Supply, cold ironing, has moved from a voluntary green initiative to a regulatory requirement, and the commercial and environmental case for early adoption is strengthening with every policy cycle.
What OPS does: Allows vessels at berth to shut down auxiliary engines and connect to the port electrical grid, eliminating engine emissions and noise during port stays.
Emission reductions: CO₂ reductions exceeding 57% achievable when powered by renewable energy; NOx and SOx reduced by approximately one third. The Port of Kaohsiung recorded an 8.7% NOx and 11.74% SO₂ reduction attributable to OPS.
Regulatory mandate: The FuelEU Maritime Regulation, effective January 1, 2025, mandates OPS use at EU ports, with non-compliance resulting in fines or port access restrictions.
Power demand: Vessels at berth require between 2 and 12 MW of shore power, requiring significant infrastructure planning and grid capacity investment by port authorities.
US adoption: California’s At-Berth Regulation drives OPS implementation across six state ports; expansion programmes are underway in Galveston, Miami, and Philadelphia.
Investment case: Despite high initial infrastructure costs, OPS lowers fuel and maintenance expenditure over time, and early adoption accelerates return on investment by securing infrastructure access ahead of regulatory deadlines.
What OPS Is and Why It Matters
Onshore Power Supply, known in the industry as cold ironing or Alternative Maritime Power, is the practice of connecting a vessel at berth to the port’s electrical grid, allowing its auxiliary engines to be shut down entirely during the port stay. Those auxiliary engines, which would otherwise run continuously to power lighting, ventilation, refrigeration, and onboard systems, are a significant source of localised air pollution at ports. Particulate matter, nitrogen oxides, sulphur oxides, and carbon dioxide emitted at berth affect port workers, nearby communities, and coastal ecosystems in ways that are both well-documented and increasingly unacceptable to regulators and communities on which ports depend for their operating licences. OPS eliminates that emission source at its root, replacing engine combustion with grid electricity that can increasingly be sourced from renewable generation.
The environmental case has been understood for decades, but OPS historically struggled with the capital investment required, compatibility challenges between vessel electrical systems and port infrastructure, and the absence of regulatory compulsion to drive adoption. That picture has changed materially. The FuelEU Maritime Regulation, which took effect in January 2025, mandates OPS use at EU ports and introduces fines and port access restrictions for non-compliant vessels and operators. Cold ironing has moved from a voluntary sustainability credential to a compliance requirement, and the infrastructure investment required to meet that requirement is now a strategic priority for ports and shipowners alike.
Operators who invested early in OPS infrastructure and vessel retrofits are now positioned to meet the FuelEU Maritime mandate without disruption, and to benefit from the lower fuel and maintenance costs that accrue from every hour an auxiliary engine remains shut down at berth.
The Environmental and Operational Benefits
The Regulatory Landscape
The FuelEU Maritime Regulation that entered into force in January 2025 represents the most significant regulatory driver for OPS adoption in Europe. It mandates that vessels use shore power while at berth at EU ports, with non-compliance triggering financial penalties and potential restrictions on port access. The regulation also introduces monitoring and reporting requirements for energy use at berth, creating a transparency obligation that will make OPS performance visible across the fleet.
FuelEU Maritime compliance deadline: The January 2025 effective date means vessels calling at EU ports are already subject to OPS requirements. Operators without compliant shore power connection systems, and ports without the infrastructure to support them, are already in non-compliance territory. Public funding mechanisms are available in some EU jurisdictions to offset infrastructure investment costs. Operators should engage with port authorities and national maritime administrations immediately to understand what support is available and what timelines apply.
In the United States, California’s At-Berth Regulation has been the primary driver of OPS adoption, mandating shore power use at six major California ports for container, cruise, and refrigerated cargo vessels. Expansion programmes at ports in Galveston, Miami, and Philadelphia reflect the regulatory trajectory: what begins in the most stringent regulatory jurisdictions tends to set the standard that others follow. Operators who have invested in OPS infrastructure and vessel retrofits ahead of mandatory requirements are positioned to call at these ports without compliance risk.
Challenges and Practical Considerations
The barriers to OPS adoption are real. The initial capital investment required, for port-side electrical infrastructure, vessel connection systems, and any necessary grid upgrades to handle the 2 to 12 MW power demands of berthed vessels, is substantial. Economic analyses of the full lifecycle cost-benefit for individual shipowners are less available than the industry needs, making investment decisions harder to justify without clear financial models. Compatibility between the electrical systems of different vessel types and standardised shore connection infrastructure requires careful technical coordination, and the shift toward alternative fuels on some vessel types introduces additional complexity around what shore power infrastructure will ultimately be needed.
The investment case for OPS isn’t simply about compliance. It’s about securing infrastructure access before demand outstrips port capacity, reducing long-term operational costs, and positioning vessels and port facilities for the next wave of environmental regulation rather than being caught behind it. Early movers accrue advantages that late movers must pay to replicate.
Community engagement is a consideration that port authorities are increasingly recognising as essential to successful OPS infrastructure development, particularly where projects involve renewable energy generation on or near port land. Navigating planning processes, addressing community concerns about visual impact and land use, and communicating the air quality benefits of the project to local stakeholders are all components of successful infrastructure delivery that purely technical approaches to OPS planning can overlook.
Frequently Asked Questions
What is cold ironing and why is it called that?
Cold ironing is the practice of connecting a vessel at berth to the port’s shore power supply, allowing its auxiliary engines to be shut down. The term originates from the era of steam-powered ships, when the iron of the engines and boilers would literally go cold when shore power was connected and the vessel’s own machinery was no longer running.
Does OPS require special equipment on the vessel?
Yes. Vessels require compatible shore connection systems, including standardised connection cables, converters where the vessel’s onboard frequency or voltage differs from the port supply, and the electrical switchgear to transfer load safely from auxiliary engines to shore power. Retrofitting existing vessels is technically feasible but carries cost and complexity that varies by vessel type and age.
What is the FuelEU Maritime Regulation and when does it apply?
FuelEU Maritime is an EU regulation that entered into force on January 1, 2025, mandating the use of onshore power supply at EU ports for vessels above a defined size threshold. It also introduces greenhouse gas intensity limits on the energy used by ships calling at EU ports, with compliance assessed on an annual basis and non-compliance subject to financial penalties.
How much can OPS reduce emissions?
The emission reduction depends significantly on the carbon intensity of the grid electricity used. When powered by renewable energy, CO₂ reductions exceeding 57% are achievable compared to auxiliary engine operation. NOx and SOx reductions of approximately one third are typical. The Port of Kaohsiung documented 8.7% NOx and 11.74% SO₂ reductions attributable to its OPS programme.
Sources: FuelEU Maritime Regulation (EU) 2023/1805 · California Air Resources Board At-Berth Regulation · Port of Kaohsiung OPS emission reduction data · European Commission alternative fuels infrastructure and shore-side electricity guidelines · IMO MEPC maritime decarbonisation strategy documentation
