Harmonic issues in power systems are becoming an important topic for industrial customers and power suppliers alike due to their adverse effects in both consumer appliances as well as for utility suppliers. Consumers should seek to reduce harmonic pollution, regardless of voltage or current distortion already present in the network. This article suggests a new method for suppressing distortions by using the non-linearity current index (NLCI) to determine the shunt single-tuned passive filter (STPF) compensator value in non-sinusoidal power systems, with the objective of maintaining the power factor within desired limits. The objective of the proposed method is to minimize the nonlinear current of customer’s loads in the power system at the point of common coupling (PCC). Moreover, the proposed design takes into consideration other practical constraints for the total voltage and individual harmonic distortion limits, ensuring compliance with (Institute of Electrical and Electronics Engineers) IEEE 519-2014 guidelines, maintaining distortions at an acceptable level while also abiding by the capacitor loading constraints established in IEEE 18-2012. The performance of the optimally designed compensator is assessed using well documented IEEE standards based on numerical examples of nonlinear loads taken from previous publications.