In this article, an integrated methodology is presented to assess an optimal mix and perspective development of energy generation technologies not only by technical, economic or other criteria, but also from an energy security perspective. The energy security is evaluated in terms of energy system resistance to disturbances. The methodology comprises several models, such as a stochastic model of energy systems disturbance parameters, economic-optimization model of energy systems functioning, metric and analysis techniques of energy security. The perspective development and functioning of the energy systems with stochastic disturbances is modelled using economic-optimization model with the development of different energy generation technologies. An open source energy modelling system is used as a tool for this model. The concept of energy security coefficient, which is calculated to assess energy security in terms of energy price increase and the amounts of unsupplied energy due to the disturbance consequences, is presented in the article as well. The developed methodology is applied to the case study of the reference energy system. Its various development scenarios with different energy generation technologies are analysed according to the share of technologies in the energy production. Scenarios are simulated in the stochastic environment of various disturbances and results are obtained in terms of variation of energy security coefficient over time by comparing scenarios from the energy security point of view. Finally, the results of the development scenarios are discussed, threshold shares in the energy production and optimal mix of energy generation technologies in terms of energy security are proposed, limitations of the case study are identified and some general conclusions are given. (C) 2014 Elsevier Ltd. All rights reserved.