Solar panel output calculator
Nameplate power is measured at 1000 W/m2 and 25 degrees. Real output is that, times the hours of full sun, times everything that goes wrong.
W
h
%
Covers inverter losses, soiling, temperature, wiring and mismatch. 75 to 85% is typical.
per kWh
Annual generation
6136kWh
- Average daily generation
- 16.800 kWh
- Average monthly generation
- 511.4 kWh
- Value at your electricity price
- 1718.14
- Specific yield
- 1227 kWh per kWp
- Capacity factor
- 14.00 %
Show the working
- Array size = 5000
- Peak sun hours per day = 4.2
- System derating = 80
- Electricity price = 0.28
- Average daily generation = 5000 * 4.2 * 80/100 / 1000 = 16.8
- Average monthly generation = 16.8 * 30.4375 = 511.35
- Annual generation = 16.8 * 365.25 = 6136.2
- Value at your electricity price = 6136.2 * 0.28 = 1718.14
- Capacity factor = 5000 > 0 ? 6136.2 / (5000/1000 * 8766) * 100 : 0 = 14
- Specific yield = 5000 > 0 ? 6136.2 / (5000/1000) : 0 = 1227.24
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
Scenarios & local history
Compare a saved scenario
Recent calculations
The formula
- daily kWh = array watts x peak sun hours x derating / 1000
- capacity factor = annual generation / (rated power x 8766 hours)
Peak sun hours is the number of hours of 1000 W/m2 that would deliver the same daily energy — typically 2.5 in northern Europe and 5.5 in the US southwest.
Panels lose about 0.4% of output per degree above 25 C, which is a large part of the derating figure.