How much electricity a panel will produce in your region. Based on real sun position, climate statistics and temperature losses.

Model: sun position from the NOAA algorithm, sunrise and sunset including refraction (−0.833°), Kasten–Young air mass, Erbs beam/diffuse split, HDKR (Hay–Davies–Klucher–Reindl) transposition to the tilted plane, NOCT cell temperature, 14% system losses (inverter, wiring, soiling, mismatch). Cloud attenuation follows Kasten–Czeplak and is calibrated so that the annual irradiation matches the measured climate normal of the region; the statistics of clear, partly cloudy and overcast days are annual, without a monthly cycle. Deviation from PVWatts/PVGIS benchmarks about 5%. Snow cover enters only through the ground albedo (0.2 → 0.65); snow lying on the modules, shading and degradation are not included.