Distributed photovoltaic (PV) and battery energy storage (BES) generating systems are interesting to power utilities owing to their benefits in terms of technology, business, and the environment. However, improper distributed generation (DG) sizes and locations might have an impact on the technological distribution network. The aim of this study is to improve the production of grid-connected PV on the electrical three-phase poles of a low-voltage distribution system for a period of 25 years. This improvement will be explored both without and with the inclusion of decentralized BES (DeBES). The purpose of this comparison is to assess the absence of power injection into the LV and MV grids by PV over a 25-year period of planning studies. This assessment will focus on evaluating energy loss and voltage profiles, utilizing DeBES in the radial unbalanced LVAC distribution system. The first step involves identifying the radial topology and phase connections within the target area. This includes assessing the performance using an unbalanced load flow analysis, which is based on the forward-backward sweep technique. Next, the water cycle algorithm (WCA) is implemented to determine the optimal locations and sizes of PV generation at the electrical poles of the system. Next, the DeBES is used to store the residual energy from the PV integration to supply power back into the grid when PV production is not available. A study site was located in a rural village area in Cambodia. Finally, the simulation results of system performances with the proposed method are discussed and analyzed in the planning procedure. The implementation demonstrated that the installed DeBES system with distributed PV can be further enhanced in both scenarios. This can be achieved by attaining zero integration into the LV and MV grids, achieving the highest reduction in energy loss, and maintaining voltage within the operational topology limit. However, a techno-economic analysis was conducted to calculate the total expenditure (TOTEX) in the case with PV. This analysis aimed to determine the optimal approach, considering environmental factors.