This paper proposes a method for the economic evaluation of an autonomous independent network of distributed energy resources. There are existing proposals for such networks; the system that we are proposing and analyzing in this study is called Microgrid. Microgrid is a new framework of power delivery system that is formed by small, modular generation systems connected to each other to create a small autonomous grid. This paper estimates the total costs to consumers in a Microgrid with optimized operation of distributed generators and energy storage systems. This estimation includes not only installation and operation costs but also the additional expenses to construct the Microgrid itself. In addition, power interruption costs are also taken into account to consider the reliability enhancement created by the Microgrid. The paper attempts to determine whether or not it is economical for consumers to form this kind of autonomous independent network.