Calculate annual energy production in kWh from solar panel size and peak sun hours (typical values included), or from a capacity factor or wind speed.
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Annual Energy Production Formula
Choose production by capacity factor, solar peak sun hours, or either simplified wind model; measured capacity factor; or required system capacity from a target. Select a 365- or 366-day year.
Solar PV using peak sun hours
- AEP = annual energy production in kWh for the selected year
- P = solar system size in kW
- H = peak sun hours per day
- D = operating days per year
- L = system losses as a percent
- G = annual degradation as a percent
- Y = year number after installation
Production using capacity factor
- AEP = annual energy production in kWh for the selected year
- P = solar system size in kW
- year hours = 8,760 for 365 days or 8,784 for 366 days
- CF = capacity factor as a percent
- L = system losses as a percent
- G = annual degradation as a percent
- Y = year number after installation
Wind production
The Weibull scale is mean wind speed / Gamma(1 + 1/k). The curve model is zero below cut-in and above cut-out, cubic between cut-in and rated speed, and capped at rated power. The rotor model uses min(rated power, 0.5 ร air density ร swept area ร Cp ร wind speedยณ), with the same cut-in/cut-out limits. Rotor Cp gives mechanical power; include electrical conversion losses in total losses. These simplified models do not replace a manufacturer curve or site assessment.
Capacity and capacity factor
Capacity factor (%) = measured kWh / (rated kW * year hours) * 100 Required kW = target annual kWh / annual yield per kW
Energy unit relationships
- Amount = energy value entered
- Source Factor = number of kWh in one source unit
- Target Factor = number of kWh in one target unit
- Converted Energy = equivalent amount in the selected target unit
Unit selections convert capacity to kW and energy to kWh. Capacity-factor inputs already reflect losses. Solar and wind modes apply the separately entered loss fraction. Optional lifetime estimates sum first-year energy ร (1 โ G/100)^(j โ 1) over whole years j. Optional energy value uses a constant entered USD/kWh price; emissions and household comparisons use entered factors.
Typical Solar and Energy Reference Values
These illustrative values vary by site and system. Use measured local data and project-specific assumptions.
| Input | Typical range | Notes |
|---|---|---|
| Peak sun hours | 3 to 6 h/day | Lower in cloudy or northern locations, higher in sunny desert climates. |
| Solar PV system losses | 10% to 20% | Includes inverter loss, wiring loss, soiling, shading, and temperature effects. |
| Solar PV capacity factor | 12% to 25% | Represents actual annual output compared with running at full power all year. |
| Annual degradation | 0.3% to 0.8% per year | Solar panels usually produce slightly less energy each year. |
| Energy unit | kWh equivalent | Common use |
|---|---|---|
| 1 Wh | 0.001 kWh | Small electronics and battery ratings |
| 1 MWh | 1,000 kWh | Large solar systems and utility billing |
| 1 Btu | 1 / 3,412 kWh | Heating and cooling energy |
| 1 joule | 1 / 3,600,000 kWh | Physics and engineering calculations |
| 1 therm | About 29.31 kWh | Natural gas energy comparison |
Example Calculations
Example 1: Solar PV annual production
You have a 6 kW solar PV system, 4.5 peak sun hours per day, 14% system losses and 365 operating days.
The estimated annual energy production is about 8,475.3 kWh in year 1.
Example 2: Capacity factor
A 1,000 kW system operating at a 35% net capacity factor over 8,760 hours produces 1,000 ร 8,760 ร 0.35 = 3,066,000 kWh. Conversely, that measured output gives a 35% capacity factor. Losses are not subtracted a second time.
FAQs
What is annual energy production?
Annual energy production is the amount of energy a system produces or uses over one year. For solar PV, it usually means yearly electricity output in kWh. For an appliance, it means yearly electricity consumption in kWh.
What is the difference between peak sun hours and capacity factor?
Peak sun hours describe the average usable solar energy received per day. Capacity factor describes annual output as a percentage of the maximum possible output if the system ran at full rated power every hour of the year. Use peak sun hours when you have daily solar resource data. Use capacity factor when you have annual performance data or want a broader estimate.
Why is my solar production lower after entering degradation?
Degradation accounts for the gradual loss of solar panel output over time. A 0.5% annual degradation rate means the system is modeled as producing 0.5% less each year after the first year. Enter a whole project life to show lifetime production, average annual output and final-year output; the main result remains first-year production.
