An evaluation of the existing hydrothermal energy economics related quantitative studies is provided. The objective is to present the similarities and differences in methodology and assumptions, and explain the impact of these differences on the energy price estimates. A brief summary of the study categories, economic evaluation methodology, technical and economic assumptions and major outputs of the studies is presented. The relative importance and the likely effects of the most important technical and economic factors on the cost of energy are discussed. The sensitivity analysis results provided are useful in judging the credibility as well as the relative weaknesses and strengths of the various cost of energy estimation studies. The major conclusions of the evaluation and the recommendations for future research are presented.