Abstract This paper investigates the performance of a radial system while installing a Distributed Generator (DG) in existing Distribution Network (DN). The investigation has been performed with various types of DG units for different topologies of the DN. The present work uses a Voltage Stability Index (VSI) for identifying the location for installing a DG in the DN. A multi-objective framework is proposed to evaluate the size of the DG to be installed by reducing power loss and deviation in bus voltage. Genetic Algorithm (GA) is used to optimize the size of DG. The proposed method has been tested with different types of DG units on standard systems (IEEE-33 bus and IEEE-69) with different radial topologies of DN.