The evaluation of investments on the expansion of power-generating capacities is a challenging one that requires consideration of many conflicting criteria and objectives. Consequently, these sorts of problems are quite suited to the use of multi-criteria decision making methods. The aim of this study is to select the best power plants among six different energy investment options, currently being planned for construction in Turkey. Decisions are made subject to a set of 17 criteria relating to technical, economic, and environmental considerations. As a methodological tool, the grey relational analysis (GRA) approach is applied to solve the presented problem. The analysis is also supported through scenarios by giving different weights to the criteria in the GRA in order to improve the quality of decision given by policy makers.