High Quality Content by WIKIPEDIA articles! Shorepower (also known as cold ironing, Alternative Maritime Power, shore power or shore supply) is the provision of shoreside electrical power to a ship at berth while its main and auxiliary engines are turned off. Cold ironing is not common on merchant ships as it involves switching off all its independent internal power sources when in harbor. While the term denotes shore as opposed to off-shore, it is sometimes applied to aircraft or land-based vehicles (such as campers, heavy trucks with sleeping compartments and tour buses), which may plug into grid power when parked for idle reduction.