A study has been conducted to develop a model for comprehensively analysing national power mixes. The objective of this paper is to show the results of the environmental dimension of this research, which considers the most usual power generation technologies in Spain, covering over 90% of the annual demand coverage. The proposed methodology is based on a two-phase process for the technology evaluation. An AHPAnalytic Hierarchic Process (AHP) is used in the first phase to calculate weights for each criterion and subcriterion. This makes it possible to rank technologies in a first comparative order. In the second stage, a fuzzy inference systemFuzzy Inference System (FIS) is used to create unique fuzzy assessments of each technology using the weights of the criteria previously determined by the AHPAnalytic Hierarchic Process (AHP). The findings indicate that CO2 emission is the key factor among the environmental variables taken into consideration and that photovoltaic technology has the highest environmental rating, while coal receives the lowest position.