A new hybrid approach has been applied to determine the optimal location and size of shunt capacitors to improve the power factor (PF), enhance the voltage profile (VP), and consequently reduce total active and reactive power losses in the Radial Distribution System (RDS). This paper proposes a hybrid approach combining Reactive Power Flow Analysis (RPFA), Weak Bus Identification (WBI), and the Particle Swarm Optimizer (PSO) algorithm, the RPFA-WBI-PSO. Indeed, the RPFA-WBI index identifies the network nodes most sensitive to the addition of capacitors, while the PSO algorithm optimizes their sizes. The proposed approach was evaluated on 10- and 33-bus RDSs to assess its performance compared to other methods in the literature. The RPFA-WBI-PSO method presents a percentage reduction in active power loss of 14.09% for the 10-bus RDS and 34.95% in the case of the 33-bus RDS.