Solar Panel Output

How it works

daily Wh = panel W × panels × peak sun hours × (1 − losses)

Peak sun hours are the day’s solar energy expressed as hours at 1000 W/m², numerically equal to kWh/m²/day. Look them up for your location and month (for example on the EU’s PVGIS or NREL’s PVWatts). Typical yearly averages run from about 2.5 in northern Europe to 6 in desert regions, and winter values can be a third of summer ones.

Losses cover heat (panels lose ≈ 0.4 %/°C above 25 °C), wiring, dust, mismatch and the charge controller: 15–25 % is a sensible default.

References

• PVGIS (EU Joint Research Centre)
• PVWatts (NREL)