Journal of the Korean Solar Energy Society ISSN:1598-6411(Print) 2508-3562(Online) 한국태양에너지학회 논문집

In this study, we estimate the cost-parity energy price and the internal rate of return (IRR) when replacing Korea Electric Power Corporation (KEPCO) retail tariffs with direct power purchase agreements (direct PPA) amid the expansion of RE100 requirements and rising electricity prices. Methodologically, we defined the peak solar generation window using nationwide average daily solar hours and solar noon time. We then matched KEPCO time-of-use (TOU) rates with the type of day and derived final payable amounts by incorporating the full cost items of ON- and OFF-SITE direct PPAs. Finally, we evaluated 20- and 25-year IRRs. The results show that for industrial (B) high-voltage systems, the ON-SITE cost-parity price of KRW at 192 / kWh yielded IRRs of 13.57% (20-year) and 14.15% (25-year). Furthermore, seven of the nine industrial (B) tariffs have cost-parity prices above the RPS fixed-price cap (KRW 156 / kWh). ON-SITE outperformed OFF-SITE in profitability and substituting industrial (B) tariffs with direct PPAs was economically more favorable than substituting General (B) tariffs. This study provides practical benchmarks and targets for direct PPA design by local governments and corporate RE100 procurement.