The paper applies the multi-level perspective (MLP) in a descriptive study of three Norwegian ports, to shed new light on the sociotechnical processes that structure their efforts to develop into zero emission energy hubs. While exogenous pressures cause tensions over port governance, the studied ports utilize their full spectre of functions; as landlords, operators, authorities and community managers, to enable transition. The respective approaches vary, related to their local context, market situation and social networks, including port's relations with their owners. Individual orientations and organizational capacity further influence their engagement with radical innovation niches (e.g. OPS, hydrogen, LNG). The study highlights the active role of ports in sustainability transition. It shows how the interaction between geographical factors and institutional work influences the scope for new solutions around the individual port, and how this makes for different feedback loops and contributions to sustainability transition in wider transport and energy systems.