The technology of cold ironing (or shore-to-ship power) can meaningfully reduce greenhouse gases and air pollutant emissions from ships at the berth by powering the vessels from the electrical shore grid. While cold ironing constitutes an effective and affordable solution in northern Europe and America, economic, legal, and environmental factors still render this technology less attractive in southern Europe. This paper aims to unpack and analyze the economic, regulatory, and environmental factors that can foster cold ironing as a standard installation in the Mediterranean Sea. Based on a model design for the port of Trieste (Italy) as applied to a cluster of target ports in the Adriatic Sea (in Italy, Croatia, and Greece), this article evaluates the cold ironing payback period by comparing costs of shore side-plants with environmental externalities and O&M costs. Moreover, the paper addresses key regulatory bottlenecks arising in different European jurisdictions with regard to the setting-up and development of cold ironing, while appraising the legal and economic consequences of deploying cold ironing in light of the future inclusion of the maritime sector in the EU Emission Trading System.