This paper proposes a methodology to assess the technical and economic impacts of interconnecting Distributed Generation, with the possibility of islanding operation, directly in the customers of the distribution systems. This methodology allows to evaluate the effects on the reliability indexes of the distribution systems due to the interconnection of these kind of generation sources. Besides, it allows to determine the period time in which a customer retrieves the investment costs of the Distributed Generation installed, depending of the technology used. This methodology evaluates the feasibility of Distributed Generation interconnection by a balance between performance and costs. The methodology was applied to a test distribution system, operating under the technical and regulatory Colombian conditions, showing interesting results.