Diesel power systems have been widely applied for energy supply generation. This power scheme however requires periodical maintenance and contributes to the emissions of greenhouse gases. These challenges may be mitigated by integrating existing diesel station with renewable energy (RE) technologies into a hybrid system. Integration of diesel plants with RE systems has been mostly implemented using software and mathematical programming approaches, where the focus of the study is mainly on grid-independent hybrid system. Grid-connected hybrid systems have the potential to supply electricity at a lower cost in comparison to the standalone hybrid power systems. This work aims to design a system that integrates diesel plant with RE technologies into grid-tied hybrid system using insight-based Power Pinch Analysis (PoPA) method. The interactions between diesel generator, RE sources and the grid in meeting the load demands were considered in the methodology development. Various load sharing scenarios between the multiple generation sources were assessed to establish the optimal system operation. Economic assessment was performed to ensure the trade-off between the costs of generation sources and grid electricity cost can be maximized. Based on the demonstrated Illustrative Case Study, load sharing based on peak/off peak period contributes to the lowest net present cost of MYR 32,813,708, hence is deduced as the optimal on-grid hybrid diesel RE system.