Voltage regulation (VR) and energy loss minimisation have always been major concerns for distribution network (DN) operators, thereby many conventional VR schemes are dedicatedly employed in existing DNs. In this study, optimal integration of different distributed energy resources (DERs) is investigated in coordination with existing VR scheme, i.e. on-load tapchanger. To show the superiority of the proposed DER integration model, optimal allocations of different DERs are determined with and without considering the coordinated effect of existing VR schemes for annual energy loss minimisation under different scenarios. To solve this complex optimisation problem, the improved genetic algorithm (GA) is adopted. A dynamic node priority list (DNPL) is suggested to further improve the performance of GA. To validate the proposed strategy and DNPL, the DER integration problem is solved for benchmark 33-bus and real-life 108-bus Indian radial distribution systems. The simulation results are found to be inspiring when compared with the existing optimisation techniques and DER integration models without considering VR schemes.