Calculator Inputs
The page uses a single-column flow overall, while the calculator fields use a responsive 3-column, 2-column, and 1-column layout.
Example Data Table
| System Size | Sun Hours | PR | Total Losses | Forecast Days | Average Daily Output |
|---|---|---|---|---|---|
| 8.0 kW | 5.5 h/day | 82% | 19.5% | 14 | About 27 to 31 kWh |
| 12.0 kW | 6.2 h/day | 84% | 16.0% | 30 | About 51 to 57 kWh |
Formula Used
Baseline Daily Output (kWh) = System Size × Sun Hours × Module Factor × Inverter Efficiency × Performance Ratio × Tilt Factor × Seasonal Factor × Availability × Loss Factor × Degradation Factor
Module Factor = Module Efficiency ÷ 20, limited between 0.75 and 1.25
Loss Factor = 1 − (Shading + Soiling + Temperature + Wiring + Mismatch losses)
Degradation Factor = 1 − Annual Degradation × (Forecast Days ÷ 365)
Daily Forecast = Baseline Daily Output × Weather Factor
Total Forecast Energy = Sum of all daily forecast outputs over the selected period
The weather factor is generated from the irradiance variability input, creating a deterministic day-by-day forecast pattern for charting, export, and scenario comparison.
How to Use This Calculator
- Enter the DC system size and average daily sun hours for your site.
- Set technical modifiers such as module efficiency, inverter efficiency, and performance ratio.
- Add tilt, seasonal, and availability percentages to reflect your system conditions.
- Enter expected losses from shading, soiling, heat, wiring, and mismatch.
- Choose the forecast period and irradiance variability for daily weather swings.
- Optionally add a grid value rate and CO₂ factor for financial and environmental outputs.
- Press Forecast PV Output to display results above the form.
- Download the summary and daily forecast using the CSV and PDF buttons.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates baseline daily production, day-by-day forecast energy, monthly and annual equivalents, forecast value, CO₂ reduction, and a variability-based confidence band.
2) Why is performance ratio included?
Performance ratio captures real-world system behavior beyond nameplate size. It helps account for conversion inefficiencies, operating conditions, and site-specific performance gaps.
3) Should I enter all losses separately?
Yes. Separate entries make scenario testing clearer. You can see how shading cleanup, cooler modules, or better wiring directly improve expected output.
4) What does the irradiance variability input do?
It controls the daily weather factor applied to the baseline output. Higher variability produces wider swings between stronger and weaker generation days.
5) Is this a replacement for bankable solar modeling?
No. It is a planning calculator for quick comparisons. Detailed project finance or engineering studies still need measured weather data and professional simulation tools.
6) Why does module efficiency affect output?
The model converts module efficiency into a bounded performance factor. That makes efficiency useful for comparing stronger and weaker module assumptions without letting output become unrealistic.
7) What is the capacity factor result?
Capacity factor compares your average daily output against theoretical full-power operation across 24 hours. It is helpful for benchmarking systems across climates and configurations.
8) Can I use this for off-grid systems?
Yes, for generation planning. However, battery sizing, autonomy days, charge controller limits, and load timing should be modeled separately for complete off-grid design.