<![CDATA[Retrofitting existing geothermal power plants offers an opportunity to increase electricity generation without requiring additional land development while contributing to carbon emission reduction. This study evaluated the economic feasibility and avoided carbon emissions of a geothermal power plant retrofit using an integrated ARIMA–Monte Carlo approach. Historical electricity generation data from 2012 to 2025 were analyzed using an ARIMA(0,1,1) model, with projections covering 2026–2039. The forecast results were incorporated into a discounted cash flow analysis using the Net Present Value (NPV), Internal Rate of Return (IRR), Payback Period, and Levelized Cost of Energy (LCOE). The uncertainty was evaluated using a Monte Carlo simulation with [N] iterations. The ARIMA model achieved a Mean Absolute Percentage Error (MAPE) of 1.84% based on walk-forward validation and estimated additional electricity generation of approximately 160,167 MWh per year. The integrated analysis resulted in an average NPV of USD 11.59 million, IRR of 13.60%, Payback Period of 6.12 years, and LCOE of USD 0.0614/kWh. The simulated NPV ranged from USD 10.91 million at P10 to USD 12.28 million at P90. The retrofit was estimated to avoid approximately 131,817 tons of CO₂ emissions annually compared with the JAMALI grid emission factor, whereas the direct geothermal emissions were approximately 7,528 tons CO₂ per year. The retrofit LCOE was approximately 13.5% lower than the 2023 global weighted-average geothermal LCOE reported by IRENA, indicating economic feasibility and competitive cost performance.]]>
