Autonomous Demand Side Management is one of the major research areas that gains great attention with formation of Smart Grid. In the case of ADSM, each consumer minimizes his bill by scheduling his consumption patterns. In this thesis, the problem is studied for a model that consists of a set of retailers that sell energy to some consumers. For this system, the behavior is modeled with the Stackelberg game. In this game, the retailers as leaders, announce their cost functions to the consumers. Then each consumer a follower calculates his best load profile which leads to minimum cost. First, the problem is studied for a grid system with no constraints. In this basic model, it has been shown that retailers can gain more benefits by selecting same parameters. Then we considered another unit in a system as a regulator to control retailer’s behavior. In this new model, the profit margins of retailers become zero. In the last model, we considered a linear utility function for consumers. So each consumer tries to schedule his consumption pattern to be able to buy more energy with his budget ceiling. In this model, we showed that by increasing energy demand of each consumer, a bill will increase rapidly. However, because the retailers are reluctant to share their cost parameters with each other, an algorithm was proposed to be implemented in smart grid. Our simulation shows that the algorithm always converges to the Stackelberg equilibrium point of the game. Using simulations, We showed that an increase to the number of retailers will be beneficial to consumers because they can buy energy at lower cost. Finally, to consider the effects of retailers' contracts on the system behavior, the utility functions are modified and the results are depicted.