As the nexus between sustainability, economic efficiency and energy security becomes closer, the creation of reliable and accessible power systems becomes critical. This study seeks to find, analyse and synthesize information from various sources to assess the structure of electricity generation in order to create information technology for diversification and optimization of the energy portfolio/mix. This is essential in order to ensure electricity supply (generation) stability and reliability, guarantee power quality for the end users of electricity. With the goal of optimising and managing the structure of electricity generation mix for electricity providers, our research focuses on combining different electricity generation technologies, maximising the value of the portfolio, e.g. ensuring energy security, and minimising the portfolio’s environmental footprint. One of the major findings is that the most effective and optimal scenario for energy mix development does not always coincide with the policies of the governments and companies’ strategies. The paper presents also the difference between the current and future optimal mix.