Modern solar panels degrade at 0. 7% annually according to NREL's 2024 comprehensive study of over 54,000 systems. This calculator helps homeowners and solar engineers estimate solar panel degradation over time and predict total kWh loss throughout the system lifespan. 7% per year, significantly. PV system losses have a substantial impact on the overall efficiency and output power of solar panel arrays. Good solar design takes into account 10 main PV losses, while best design and installation practices help to reduce solar cell power losses. System loss is the energy loss in the system due to factors like inverter inefficiency, cable losses, dust, and. This table is available for both yearly and monthly losses and breaks down how incoming solar energy is reduced by various losses throughout the PV system: Input and optical losses: Shows the initial irradiation values and stepwise reductions from shading, soiling, angular, and spectral effects, on.