Demand response programs are an important resource which can significantly increase the efficiency of future smart grids. However, preliminary experiences evidence some difficulties in making the use of these programs successful, and also increased difficulties in extending them to include relevant participation of small consumers. This paper proposes a distributed agent-based intelligent system to model and simulate a smart grid with a diversity of players, each one with his own specific configuration and goals. This system accommodates the use of physical players, e.g., real electrical installations, as well as computationally simulated agents. This paper presents the capacities of the proposed system to simulate the use of demand response programs. The system allows assessing the impact of these programs to the involved consumers, to the other players and to the whole system. In this way, the alternative demand response program structure and parameterization can be simulated and evaluated.