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Solar panel output calculator

Estimate solar array output per day, month and year from panel watts, count and peak sun hours after inverter, temperature and system losses.

Enter a panel rating, a count, and your peak sun hours.

The estimate multiplies array kilowatts by your sun hours and then by the loss stack, PVWatts style. It assumes well-mixed shade and average weather; shading on one string at midday can dwarf the whole loss table, and a flat temperature percentage under-models hot climates. Nothing is looked up for you: sun hours vary with tilt, azimuth and season, so enter your own figures. Averaged sizing also misses the worst month, which is what the monthly table is for. This is an estimate, not a site survey or a guarantee.

Array and losses

Panel rating (W)

Number of panels

Peak sun hours a day

Target use (kWh/day), optional

Inverter efficiency (%)

Temperature loss (%)

More settings

Monthly sun hoursOptional, twelve values; empty uses the daily figure all year

Soiling loss (%)

Wiring loss (%)

Connections loss (%)

Light-induced degradation loss (%)

Nameplate rating loss (%)

Mismatch loss (%)

Availability loss (%)

Incident angle loss (%)

Shading loss (%)

Snow loss (%)

Losses multiply, so the PVWatts defaults combine to about 14.08 percent, not 15. Sun hours are kWh/m²/day on the panel plane, from a solar map, PVWatts or PVGIS.

Panels stay between 1 and 2000 W, at most 100,000 of them, sun hours between 0 and 12, inverter 50 to 100 percent, temperature loss up to 50 percent, each loss category up to 100 percent.

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Solar panel output calculator

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