Work out solar panel sizing instantly with clear inputs, formula shown and shareable results.
Array size is daily energy demand divided by peak sun hours and by the system efficiency. Losses of 20-25% are normal and cover inverter conversion, wiring, soiling, mismatch and the fact that panels run hotter than their 25 degree test condition.
Array sizing
array W = daily Wh / peak sun hours / (1 - system losses)
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.
The equivalent number of hours at 1,000 W/m2 that delivers the day's total irradiation. It is not daylight hours — a 12 hour day may give only 4 peak sun hours.
Temperature alone costs 8-15% in warm climates, inverters 3-5%, wiring 2-3%, soiling and mismatch the rest.