Energy-related and environmental issues are getting more attention and are becoming more important over the years. Currently, they are considered as one of the greatest challenges worldwide. The widespread use of fossil fuels causes the increase of the harmful emissions which are associated with significant health and environmental issues. Ports are no exception to this problem as they are considered as major contributors. Although there are some measures available, the high majority of them focus only on technologies that can reduce the vessel emissions. The focus of this research study is on the development of a decision making tool for technologies that can be used for the reduction of the emission footprint of the ports’ shore-operations. The decision making for such technologies is not an easy process. The large number of stakeholders, the environmental concerns as well as the fast changing business environment create a complicated decision making scheme. This scheme represents specific practical and theoretical issues which need to be addressed. A list of known theories that solve these issues and a list of methods and tools that deal with values and data were used for the development.  The developed decision making tool describes a ten step approach that provides specific guidelines and sub-tools for the assessment of the port’s situation and the technologies until the final technology selection. Considering the diverse character of ports, their fast changing business environment as well as the innovations concerning the low emission technologies, this tool has no static data-input. It reacts with the business environment and provides with the best technology choice related to the values of the stakeholders at a specific moment of time. The developed tool was applied as an illustration study to the port of Piraeus for the following vision: ““Implementation of renewable energy technologies for electricity generation that can reduce the emission footprint of the Piraeus’ shore-operations”. The decision making tool can be used by port authorities either as the main decision tool or as supplementary tool that provides port authorities with an indication. The tool can be applied to all types of ports without restrictions such as the size or the economic activity. Its main characteristic is that it quantifies the decision making process by creating a “common language” for understanding the current situation in terms of decision criteria importance and technology opportunities. The application of the tool proved that it is particularly efficient for gradually identifying the values and their importance as decision criteria. The idea of dynamic input of data provides the flexibility to possible changes which consists an important aspect for making responsible decisions.