Following the global concern and IMO directives, in particular for greener shipping, ships and ports tend to become more efficient in terms of environmental friendliness, energy consumption as well as services provided. This paper deals with facing the challenges emerged within this framework, as in the ship case, certain retrofitting works have to take place onboard a ship such as the installation of water ballast treatment systems, scrubbers, cold-ironing facilities, and LED lights. The paper discusses the necessity to perform a number of studies (e.g. harmonic distortion, short-circuit, arc-flash etc) so that major safety requirements are met, while on the other hand, the electric energy system has to be tuned to a significant extent so that it operates in an optimum manner which is most often interpreted as minimum fuel consumption and emissions. Further, the paper makes a similar discussion for the case of the ports.