Sizing Photovoltaic Self-Consumption Systems through Mismatch Index and Profitability Analysis

This paper presents a methodology for evaluating and sizing photovoltaic self-consumption systems through a combined technical and economic approach. The analysis relies on hourly energy balance simulation and introduces the Mismatch Index (MI) to quantify the temporal alignment between energy availability and demand, enabling a more precise assessment of self-consumption performance. The financial analysis includes four indicators: Payback Period, Net Present Value, Internal Rate of Return, and Levelized Cost of Energy. The methodology has been applied to a real residential case using historical hourly data on consumption, irradiance, and electricity tariffs in Spain. As a result, the tool indicated a system size that achieves both technical alignment with demand and favorable economic outcomes. The proposed approach serves as a practical decision-support tool for residential PV system design, aligning energy behavior with realistic financial expectations.