This book covers available approaches to improving the performance and impact of long-term projections of the national energy sector development. In turn, it introduces an original multi-stage approach to narrowing down the uncertainty range of the input data and resulting projections. Its unique contribution is that it limits the scope for each of the projection timeframe segments step-by-step. This is done in the course of iterative calculations, which employ dedicated methods and other tools to elucidate and solve top-priority problems specific to each time segment. In closing, the book provides a detailed treatment of two essential research problems: 1) long-term forecasting for regional energy markets, and 2) the quantitative assessment of a) the barriers that are likely to hinder energy sector development and b) strategic-level energy security threats.