In the context of reducing emissions from the transport sector, the EU Commission envisions a strong modal shift to energy efficient modes including maritime shipping and inland shipping, as an alternative for road transport. In view of the expected growth of the sector, the emissions from waterborne transport are a key concern. When at berth, ships typically use their auxiliary engines to generate electrical power for communications, lighting, ventilation and other on-board equipment. The extended use of vessels' auxiliary engines augments greenhouse gas (GHG) emissions and air pollution in the adjacent ports, which are typically located in or near densely populated areas, thus leading to dangerous health and environmental effects. Shore Side Electricity (SSE) is an option for reducing the unwanted environmental impacts of ships at berth, i.e. GHG emissions, other air pollutants (NOx, SOx, PM) and noise of ships using their auxiliary engines. This paper quantifies the economic and environmental potential for SSE in Europe, through detailed estimation of in-port ships' emissions and relevant energy demand, providing an insight of the expected barriers for implementation and formulating recommendations on policy actions that could accelerate the implementation of SSE in European harbors. (C) 2015 Elsevier Ltd. All rights reserved.