The growing number of the world’s population, the scarcity of power resources and striving for the benefits offered by modern civilisation have resulted in power systems of massive dimensions. To maintain and develop these power systems, considerable investments are needed in any country. All the elements of a power system function as a united system that is largely influenced by a number of quantitative and qualitative factors of changeable nature. Since many factors cannot be measured precisely, nor even described as probabilistic values, most decisions have to be taken in the conditions of uncertainty. The growth in energy consumption, the growing dimensions of power systems, their complexity and significance, the fluctuating prices of energy resources as well as the influence of accidental factors and uncertainty — all of the above have sharpened a number of serious issues related to the power industry: power supply efficiency and reliability as well as the environmental impact and sustainability of power supply. The importance of a complex approach to power industry development issues determines the goal of the present doctoral thesis: to develop a methodology for feasibility studies of power facility projects on the basis of the game theory, with a special emphasis on using the methods of co operative game theory. The conditions for the co-operation of market participants (producers, transmission and distribution system operators and consumers) have become particularly topical after the adoption of decisions on an international scale regarding the restructuring of power systems and the introduction of free-market mechanisms to the control of power system development and operation. The present doctoral thesis formulates the task for a feasibility study; an algorithm for project substantiation is synthesized for a situation of several possible coalition founders. The rationality of supporting the actions of the initiator is proved. The task of power supply planning for independent consumers is formulated and solved, by means of forming a co-operative. A heat loads forecast for the city of Riga up to the year 2020 is substantiated. A development plan for Riga is synthesized, encompassing a prospective period till the year 2020. Also, a new methodology, suited to the market conditions, is substantiated for determining heat and electricity tariffs. The developed methodology of project feasibility studies, which applies co-operative game theory for making decisions in the power industry in the conditions of uncertainty, can be used by all the participants of the energy market, so as to achieve the most efficient use of total resources.