One of important technological issues in microgrid is to control supply and demand balance in own system. In general, the targets of the control are to adjust the outputs of the distributed generations (DGs) according to the load change and to control the tie line power flow. However, when the owners of each DG are different, it is required that the output of each DG is decided considering economic efficiency. To realize such an efficient operation of microgrid, we have developed a new demand and supply control method based on mobile agent technology so far. In this paper, we evaluate the control effect when a large amount of DGs which utilize the renewable energy are introduced in microgrid.