The Brazilian electric energy generation system is a hydrothermal system of great size, with predominance hydroelectric plants. Its peculiar size and characteristics is the only one in the world. Consequently, its coordination is very complex and, therefore, it´s necessary the correct planning and operation to prevent or reduce problems related to supplement security. In this context, this work studies the conditions that resulted in the rationing of electric energy in 2001 and in the beginning of 2002, as well as the effect in the short term and the medium term and infers on a new rationing possible. For this, energy consumption estimations were done, during the period of crisis and was developed a computational modeling to simulate its effect. To get the indicative of the last rationing and to infer on a new one was done simulations in the Computational Model NEWAVE, developed by CEPEL.