Enter system and site details
Use the fields below to model realistic production with equipment, weather, and operational derating assumptions.
Example data table
This example shows how typical assumptions convert into usable energy, savings, and environmental impact estimates.
| Panel Count | Panel Wattage | Peak Sun Hours | Net Factor | Daily Output | Monthly Output | Yearly Output |
|---|---|---|---|---|---|---|
| 24 | 450 W | 5.50 | 67.63% | 40.17 kWh | 1,205.23 kWh | 14,663.61 kWh |
| 18 | 540 W | 5.10 | 69.10% | 34.20 kWh | 1,026.00 kWh | 12,483.00 kWh |
| 30 | 410 W | 4.80 | 64.90% | 38.31 kWh | 1,149.30 kWh | 13,983.15 kWh |
Formula used
DC Size (kW) = Panel Count × Panel Wattage ÷ 1000
Net Factor = Performance Ratio × Inverter Efficiency × (1 − Shading Loss) × (1 − Temperature Loss) × (1 − Soiling Loss) × (1 − Wiring Loss) × Availability × Orientation Factor
Daily Production (kWh) = DC Size × Peak Sun Hours × Net Factor
Monthly Production (kWh) = Daily Production × Days in Month
Yearly Production (kWh) = Daily Production × 365
Capacity Factor (%) = Yearly Production ÷ (DC Size × 24 × 365) × 100
Annual Savings = Yearly Production × Electricity Tariff
Avoided Emissions = Yearly Production × Grid Emission Factor
How to use this calculator
- Enter the total number of modules and each module wattage to define DC system size.
- Add average daily peak sun hours for the project location.
- Set performance ratio, inverter efficiency, availability, and orientation factor to reflect design quality.
- Enter realistic loss percentages for shading, temperature, soiling, and wiring.
- Add billing month days, electricity tariff, grid emission factor, and panel area.
- Press calculate to view output cards, the graph, savings, yield metrics, and downloadable reports.
Frequently asked questions
1. What does peak sun hours mean?
Peak sun hours represent equivalent full-strength sunlight received during a day. It converts changing irradiance into one easy production input.
2. Why use both performance ratio and separate losses?
This approach helps model overall system quality and site-specific penalties separately. It gives more control during feasibility checks and sensitivity analysis.
3. What is a good capacity factor for solar?
Good values depend on climate, tilt, and equipment. Many rooftop systems fall roughly in the low-to-mid teens, while strong sites may perform higher.
4. Should I use monthly or yearly output for planning?
Use monthly output for bills, storage sizing, and seasonal comparisons. Use yearly output for return analysis, targets, and long-range benchmarking.
5. What does specific yield show?
Specific yield measures yearly energy produced per installed kilowatt. It helps compare sites and designs without system size distorting results.
6. Why include a grid emission factor?
The emission factor estimates avoided carbon dioxide by replacing grid electricity. It is useful for sustainability reports and environmental impact summaries.
7. Can this calculator replace detailed simulation software?
No. It provides a fast planning estimate. Bankable studies still need detailed weather files, hourly modeling, shading analysis, and equipment-specific assumptions.
8. Why does orientation factor matter?
Orientation factor adjusts for roof azimuth and tilt quality. Poor alignment reduces received sunlight, even when all other losses remain unchanged.