Estimate daily and monthly energy output from a solar panel system.
Accounts for inverter and wiring losses — 75-85% is typical
Solar output depends on total panel wattage, how many peak-equivalent sun hours your location gets per day (not total daylight hours — a specific measure of usable solar intensity), and system efficiency losses from inverters and wiring.
Formula: Daily kWh = Total Panel Watts × Sun Hours × Efficiency% ÷ 1000.
'Peak sun hours' is the key variable most people get wrong — it's not the same as hours of daylight. A location might have 12 hours of daylight but only 5 peak sun hours, since it accounts for the sun's actual intensity through the day, not just whether it's up.
Ten 400W panels with 5 peak sun hours and 80% system efficiency: 400 × 10 × 5 × 0.8 ÷ 1000 = 16 kWh per day.
NREL's PVWatts tool and similar solar resource maps provide location-specific peak sun hour averages, which vary significantly by latitude and climate.
Real systems lose some energy to inverter conversion, wiring resistance, panel temperature effects, and dust or shading — 75-85% is a realistic range for a well-installed system.
No — this gives a single estimate based on the sun-hours figure you enter. Actual output varies month to month; use a seasonal average or run the calculation for different seasons separately for a fuller picture.