Solar PV System Sizing Quick Reference Guide

Solar PV system sizing is the process of selecting the appropriate number and type of PV modules, inverters, batteries (if off-grid or hybrid), and balance-of-system components to reliably supply a defined electrical load under local environmental and operational conditions. At its core, sizing begins with quantifying the daily energy requirement (kWh/day), adjusted for load diversity, future expansion, and criticality (e.g., backup vs. grid-tied). This demand is then translated into DC array capacity by accounting for location-specific solar resource data—typically using peak sun hours (PSH) derived from historical irradiance databases like NASA SSE or PVWatts—and applying derating factors for temperature, soiling, wiring losses, inverter efficiency, and module degradation. For grid-tied systems, sizing often targets net-zero annual consumption or utility-specific interconnection limits; for off-grid systems, it must incorporate battery storage capacity to cover multi-day autonomy during low-irradiance periods, requiring careful analysis of depth-of-discharge, battery cycle life, and charge controller ratings. Advanced considerations include shading analysis (via tools like Solmetric SunEye or PVsyst), voltage drop constraints, NEC-compliant conductor sizing, and local permitting requirements—each influencing final component selection and layout.