Calculator Inputs
Large screens use three columns, medium screens use two columns, and mobile uses one column.
Example Data Table
| Scenario | Array Size (kW) | Irradiance (W/m²) | Peak Sun Hours | Usable Output (kW) | Efficiency | Daily Energy (kWh) |
|---|---|---|---|---|---|---|
| Small rooftop grid-tied | 4.95 | 800 | 5.0 | 3.71 | 16.8% | 18.55 |
| Medium commercial roof | 27.50 | 900 | 5.8 | 20.91 | 17.3% | 121.28 |
| Hybrid storage system | 6.60 | 850 | 5.5 | 4.32 | 15.4% | 23.76 |
Formula Used
1) Solar Input Power
Solar Input Power (kW) = Irradiance × Total Array Area ÷ 1000
2) Total Array Area
Total Array Area (m²) = Panel Area × Number of Panels
3) Temperature Factor
Temperature Factor = 1 − ((Cell Temperature − 25) × Temperature Coefficient)
4) Usable Output Power
Usable Output = Solar Input × Module × Temperature × Shading × Dust × Mismatch × Wiring × Inverter × Battery × Availability × Other
5) Overall System Efficiency
Overall Efficiency (%) = Usable Output ÷ Solar Input × 100
6) Performance Ratio
Performance Ratio (%) = Usable Output ÷ (Installed DC × Irradiance ÷ 1000) × 100
This model estimates practical system efficiency from sunlight at the array surface to usable electrical output after major conversion and operational losses.
How to Use This Calculator
- Enter the rated wattage and total number of modules.
- Provide the module surface area and current solar irradiance.
- Add local peak sun hours to estimate daily energy production.
- Enter module efficiency and real operating cell temperature.
- Set temperature coefficient, shading, dust, mismatch, and wiring losses.
- Enter inverter efficiency and battery efficiency if storage exists.
- Set availability and any remaining system derating under other loss.
- Press Calculate Efficiency to show results above the form.
- Review the summary cards, table, and Plotly graph.
- Use the export buttons to save results as CSV or PDF.
Frequently Asked Questions
1. What does solar system efficiency mean?
It is the percentage of sunlight reaching the array that becomes usable electrical output after panel conversion, temperature effects, wiring, inverter losses, storage losses, and downtime are included.
2. Why is system efficiency lower than panel efficiency?
Panel efficiency covers module conversion only. System efficiency is lower because it also includes temperature derating, shading, dust, mismatch, cable resistance, inverter losses, storage losses, and availability effects.
3. What is a good overall system efficiency value?
Many practical systems land around the mid-teens when measured from sunlight on the array surface to usable AC output. Actual values depend on technology, climate, cleanliness, design quality, and storage configuration.
4. How should I enter battery efficiency?
Use 100% when the system has no battery. For storage systems, enter the usable round-trip efficiency of the battery path, which commonly falls below direct grid-tied conversion.
5. What is performance ratio?
Performance ratio compares usable output against expected DC production under the current irradiance level. It helps separate system losses from the basic sunlight available at the site.
6. Why does temperature reduce output?
Solar cells usually produce less voltage as temperature rises. Even with strong sunlight, hotter cells often deliver lower practical power, which is why ventilation and mounting design matter.
7. How accurate is this calculator?
It is a planning and comparison tool. Accuracy improves when inputs match field conditions, measured irradiance, equipment specifications, and realistic loss assumptions for the actual site.
8. Can I use this for rooftop and commercial systems?
Yes. The calculator works for small residential, large rooftop, and many commercial systems because it relies on general physical inputs, equipment efficiencies, and configurable loss factors.