Today, due to the increase in energy consumption and the increasing use of distributed generation units (DG) such as CHP and fuel cell (FC) units in microgrids, it is necessary to use them in the best possible conditions. The use of distributed generation units, which are mainly installed in small dimensions and on the load side of the distribution network, can provide other benefits, including reducing power transmission losses, increasing production efficiency, and increasing reliability to bring the meantime, the use of electricity and heat simultaneous production units, which are among the most widely used distributed production units, has improved the efficiency of energy production to a great extent by producing electricity and heat simultaneously, thus reducing the costs of energy failure. Therefore, in this paper, the goal is to reduce the cost of production and the cost of lack of energy supply and increase the reliability of the system. In this paper, the working modes of the sample microgrid are evaluated, and finally, the optimization of a multi-objective function, which has goals such as the economical production of each of the distributed production sources, the minimization of the cost of providing the electric and thermal energy of the microgrid, the minimization losses of electrical and thermal energy, load response program and energy storage program. The results of optimal planning of the capacity and number of co-generation units of electricity and heat under different conditions and states show the great effect of using co-generation units of electricity and heat in reducing unsupplied energy and increasing the reliability of the system.