This paper solves a daily multiobjective optimization model for efficient operation of power distribution systems. The model aims to minimize the voltage deviations, minimize power losses and minimize the energy costs of the distributed generators. The model is implemented on a modified 33 bus distribution system by including: two voltage regulators and four distributed generators. Three different simulation sets are performed: the first one includes only voltage regulators and the second one includes only distributed generators and the third one includes both voltage regulators and distributed generators. When the simulation results are compared, results show that better voltage profiles with less power losses and costs might be obtained by using both voltage regulators and distributed generators.