Size a solar array in kilowatts from annual consumption, sun hours and system losses.
Peak sun hours condense a whole day of varying irradiance into equivalent full-sun hours. The derate factor of about 20 per cent covers inverter, wiring, soiling and temperature losses. Sizing on nameplate watts without derating overstates generation by a fifth, which is the most common cause of disappointing solar performance.
Solar System Size
System kW = annual kWh ÷ (365 × peak sun hours × derate factor)
System kW = annual kWh ÷ (365 × peak sun hours × derate factor) Peak sun hours condense a whole day of varying irradiance into equivalent full-sun hours. The derate factor of about 20 per cent covers inverter, wiring, soiling and temperature losses.
Sizing on nameplate watts without derating overstates generation by a fifth, which is the most common cause of disappointing solar performance.
This calculator takes 4 inputs: Annual electricity consumption, Average peak sun hours per day, System losses, Share of consumption to offset. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.