A procedure to evaluate efficiency in the exploitation of the geographic situation of hydroelectric plants is developed here. It is based on the probabilistic composition of criteria. A comparison of 80 plants is carried out, with volume of water flow at the location and transmission rates paid measuring the potential of the geographic situation and installed power and assured energy measuring the employment of such potential. An analysis based on a new index of quality of approximation and a new measure of importance derived from Shapley value is used to select the criteria that enter a second stage of the efficiency evaluation. (C) 2008 Elsevier Ltd. All rights reserved.