Sizing Photovoltaic Self-Consumption Systems for Sustainable Decision-Making: A Novel Techno-Economic Approach Using Performance Metrics and Real Consumption Data

Photovoltaic (PV) self-consumption systems are increasingly adopted as part of the energy transition, yet residential users often lack the technical background needed to compare alternatives, particularly when storage (ST) is included. To support informed, technically consistent, and sustainable decision-making, this work presents a techno-economic tool for assessing and sizing PV self-consumption systems through hourly energy-balance simulation. Using real consumption, meteorological data, and electricity tariffs, the tool evaluates technical and economic performance and introduces the Mismatch Index (MI) to quantify the temporal alignment between PV production and demand. Combined with self-consumption (SC) and self-sufficiency (SS) metrics, MI supports consistent comparison of PV–ST configurations under real operating conditions and helps identify solutions that improve local energy use without unnecessary oversizing. The approach is applied to a residential consumer and to an energy community, comparing individual and centralized solutions. In the residential case, the selected configuration reached a SC of 87%, SS of 66%, and an IRR of 4.92%. For the energy community, the centralized solution increased the 20-year NPV from €1370 for individual systems to €20,060. Analysis of two years of hourly consumption data from 118 households indicated an uncertainty of 10–15% in average hourly consumption when one-year data is used.