Changing to green energy sources is one of the key challenges for port cities. The port authority of Rotterdam (the Netherlands) has a program to install solar panels in its own buildings and encourage port companies to do the same by providing expertise. Port and city are also working together with innovative partners like Sunrock. In other port cities, one of the main approaches to implement the energy transition is providing green electricity to ships, as it will happen in short in Lisbon (Portugal) via shore-to-ship solutions, and in Genoa and Savona (Italy) with the electrification of quays. However, the energy transition requires cooperation, as it is visible in Norway, where the seven ports of the Oslo fjord will receive financing for several projects, including shore power for ships. Another crucial aspect of the energy transition is finding alternative energy sources, as it is visible in Le Havre (France), where port and city are investing to become low carbon after the closure of its coal plant in 2021.