In this paper a model for the assessment of efficient energy generation portfolios is presented. The total energy output can consist of multiple energy carriers such as electricity, heat or chemical energy carriers. In order to take into account multiple aspects of performance and different types of incer- titude influencing the long-term energy planning process, two different methods are combined. Mean-variance portfolio theory and multi-criteria diversity analysis are applied resulting in a multi-objective optimization problem. Solving this optimization problem for multi-energy portfolios allows for identifying energy generation technologies mixes that both minimize the exposure to various kinds of incertitude and maximize performance with respect to multiple performance criteria. In this way multi-energy portfolios are analyzed in a comprehensive and systematic way.