Solar photovoltaic (SPV) energy is most promising among renewable energy (RE) sources. Outdoor performance characterisation of SPV module string using on-field test equipment with a minimum error by reducing the effect of an uncertain operating condition (OPC) is challenging. Improving PV system reliability, flexibility and reducing operation and maintenance (O&M) cost have become a significant factor in increasing the competitiveness of the PV energy market. An illustrative embodiment of literature described herein is particularly suited to select load for current-voltage curve tracer (IVCT) for varying complexities from SPV cell (few Watts) to SPV module string (up to 10 kWp).