Cold Ironing: Using Shore Power for Moored Vessels

Context of Transport Climate Action

When ships are in port, they usually generate their own electric power by running diesel-fueled power generators. This means that they are emitting exhaust gas emissions locally in the port., Using shore power instead is gaining importance, as the smoke and harmful pollutants caused by the diesel generators are unwanted in the port areas, this is called ‘cold ironing’.

‘Cold ironing’, or using shore power, is done by plugging a vessel into a power supply on the quay or shore with heavy-duty electric cables. The facilities required for cold ironing exist in several ports and are being used by a wide range of ships. In the port of Rotterdam for example there is a prohibition for inland vessels to use their power generators and all inland ships must use shore power instead of generator power. But some large luxury cruise ships also now use shore power when they are in port.


Cold ironing is the technology that allows ships to turn off their on-board power generators when in port, and to use electric energy from an on-shore supply. Because ships do not generate any exhaust gas when moored, the local air quality is improved. The carbon footprint of the electric energy that is produced on land can also be lower than the CO2 emission of the power generated on board, especially when renewable energy is used, and this can significantly reduce the amount of CO2 emitted.

Cold ironing has been analyzed from different perspectives and the research results are mostly positive when it comes to its impacts on pollutants, its effectiveness to reduce GHG emissions and its economic viability. Even though some shore power projects have been discontinued, there are numerous examples of long-term commitments to cold ironing. The West Coast ports in the state of California are an example of this where ships have been using shore power since the early 2000’s.


For cold ironing, equipment and facilities are needed. Quayside facilities include an electric grid that can provide power to the plug-in-stations and the plug-in-stations must be built on the shore side. Ships must be designed/ altered to be able to use this electric power and their electric system must be redesigned to allow this.

The implementation of shore power can be tricky due to the wide variety of power supply voltages, frequencies and plug-in systems. While several initiatives are taking place in different areas, the number of different cold-ironing methods is also increasing. Problems can occur when vessels frequent many different locations and are confronted with different cold-ironing standards. Ship operators also have some concerns about the variety of payment systems for the electric power. The administrative implications and practicalities of cold ironing are generally acknowledged as an area where there is still a large potential for improvement.

Cold ironing can be promoted by the port authorities by providing (financial) incentives such as reducing the port dues or in some case simply by making cold ironing compulsory helps ports to implement the use of shore power.


 Cold ironing has numerous benefits

  • Reducing local exhaust gas emissions (NOx, PM) which improves the port’s compliance to local emission levels
  • Reducing the negative health effects from air pollution for the people living in the vicinity of the ports
  • Reducing the CO2 footprint of the energy used by ships at berth (depending on the energy mix of the shore power)
  • Reduced noise levels in the ports and on board the ships
  • Reduced smoke and smells in the port

Potential for scaling up

Cold ironing can be used by any ship that is at berth. The availability of shore power facilities is a precondition for this. Not only ports could invest in these facilities, but privately owned freight terminals could also provide these facilities for the ships that visit their quayside. There is thus a large potential for the upscaling of cold ironing.

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Global, Mitigation, Freight, passenger, technology, policy