Calculate solar PV annual energy production, appliance electricity use, and energy unit conversions with kWh, Btu, joules, and cost.
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Annual Energy Production Formula
The calculator has three modes: solar PV annual energy production, appliance annual energy use, and energy unit conversion. Use the formula that matches the tab you are using.
Solar PV using peak sun hours
AEP = P * H * D * (1 - L/100) * (1 - G/100)^(Y - 1)
- 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
Solar PV using capacity factor
AEP = P * 8760 * (CF/100) * (1 - L/100) * (1 - G/100)^(Y - 1)
- AEP = annual energy production in kWh for the selected year
- P = solar system size in kW
- 8760 = hours in a 365-day year
- CF = capacity factor as a percent
- L = system losses as a percent
- G = annual degradation as a percent
- Y = year number after installation
Appliance annual energy use
Annual kWh = P * Q * (C/100) * H * W * 52.1429
- P = appliance power in kW
- Q = quantity of appliances
- C = percent of rated capacity used
- H = hours used per active day
- W = active days per week
- 52.1429 = average weeks per year
Energy conversion
kWh = Amount * Source Factor
Converted Energy = kWh / Target Factor
- 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
For solar PV, the calculator first converts system size to kW, applies either peak sun hours or capacity factor, subtracts system losses, and then applies degradation for the selected year. For appliances, it converts power to kW and multiplies by usage time, quantity, load percentage, and active days. For conversions, it converts the source unit to kWh first, then converts kWh into the target unit.
Typical Solar and Energy Reference Values
These values can help you choose reasonable inputs when an exact number is not available.
| 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, 365 operating days, year 1, and 0.5% annual degradation.
AEP = 6 * 4.5 * 365 * (1 - 14/100) * (1 - 0.5/100)^(1 - 1)
AEP = 8476.65 kWh
The estimated annual energy production is about 8,477 kWh in year 1.
Example 2: Appliance annual energy use
A 1,500 W appliance runs 1 hour per day, 5 days per week, at 100% capacity.
Annual kWh = 1.5 * 1 * 1 * 1 * 5 * 52.1429
Annual kWh = 391.07 kWh
At $0.15 per kWh, the annual electricity cost is about $58.66.
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. The calculator applies degradation based on the year number you enter.