In this paper comprehensive evaluations of isolated high step-up dc-dc topologies have been investigated. These converters are especially well suited for distributed generation systems utilizing renewable or alternative energy sources that need a wide input voltage range with load regulation. With this in mind, this work primarily concentrates on comparative analysis of various isolated configurations employed in possible industry applications. Consequently, several isolated structures, including flyback, forward, push-pull, and full bridge and other similar solutions have been carried out in the literature. For the purpose of comparative and theoretical analysis, some of the circuit parameters are considered, which include voltage conversion ratio, semiconductor element voltage stress, component size, and conduction and switching losses. Furthermore, the selected configurations have been discussed in terms of cost estimation and financial feasibility. In addition, the design procedure and experimental prototypes of the available solutions with the main results are presented. Derived from this investigation, the authors provide a guide to help researchers to identify different isolated topologies with wide input voltage range and galvanic isolation for prospective research directions within this area.