Distributed generators (DGs) integrated into distribution networks could affect the host network in number of ways. In this paper an assessment of the impact of the DG continuously operated, which output behavior is non-stochastic, on the reliability of supply in the industrial networks, is performed. A set of new indices representing impact of DG on the interruption frequency, interruption duration and expected energy not supplied to every single customer, is introduced. In addition, a new composite index compiling the impacts of DG on the overall reliability of supply, including interruption frequency, interruption duration and expected energy not supplied, is proposed. Results obtained from several case studies using real-life industrial network are presented and discussed.