In this report, we deal with the assessment of energy technologies using the MARKAL model. Severals methods of evaluating the relative merits of technologies are reviewed, and a comprehensive approach is recommended, that is based on two complementary aspects of the MARKAL outputs: the primal results, which describe penetration values of technologies, and the dual results, which indicate the Marginal System Values of technologies. The approach is illustrated on the result of a sample run of MARKAL-QUÉBEC.