Project Inputs
The page uses a single main content flow, while the calculator fields adapt to three columns on large screens, two on smaller screens, and one on mobile.
Example Data Table
This sample illustrates how the calculator can be used for a warehouse-scale solar planning exercise.
| Scenario | Annual Use | Peak Sun Hours | PR | Offset | Panel W | Roof Area | Estimated DC Size | Panel Count |
|---|---|---|---|---|---|---|---|---|
| Warehouse A | 250,000 kWh | 5.50 | 82% | 85% | 550 W | 1,800 m² | 182.60 kW | 332 |
| Factory B | 480,000 kWh | 5.20 | 80% | 75% | 600 W | 3,400 m² | 307.80 kW | 513 |
| Office Park C | 145,000 kWh | 4.90 | 81% | 90% | 540 W | 1,250 m² | 118.20 kW | 219 |
Formula Used
Future Load = Current Annual Use × (1 + Growth Rate)Design Years - 1
Specific Yield = Peak Sun Hours × 365 × Performance Ratio × (1 - System Losses)
Design-Year Yield = Year-One Specific Yield × (1 - Degradation)Design Years - 1
Target Solar = Future Annual Load × Target Offset
Required DC kW = Target Annual Solar ÷ Design-Year Specific Yield
Panel Count = Ceiling[(Required DC kW × 1000) ÷ Module Wattage]
Required Area = Panel Count × Module Area
Inverter AC kW = Installed DC kW ÷ DC/AC Ratio
These equations support early-stage planning. Final engineering should include tilt, azimuth, shading, structural limits, interconnection rules, demand-charge impacts, and local code requirements.
How to Use This Calculator
- Enter your facility’s annual electricity consumption from utility bills or interval data.
- Use realistic local peak sun hours rather than peak weather-day assumptions.
- Set performance ratio and additional losses to reflect site conditions.
- Choose the target offset based on budget, net metering, and operational goals.
- Enter actual module wattage and module area from the panel datasheet.
- Input usable roof area only after excluding access paths and setbacks.
- Adjust growth, design horizon, and degradation for future-focused sizing.
- Review system size, panel count, roof fit, annual output, savings, and payback.
- Export the results as CSV or PDF for internal review.
FAQs
1. What does this calculator estimate?
It estimates DC system size, inverter size, panel count, roof area use, annual generation, offset percentages, simple savings, and basic payback for commercial solar planning.
2. Is roof fit the same as a final layout?
No. Roof fit here is a quick area check. Final layout must consider setbacks, fire access, shading, obstructions, tilt, row spacing, and structural loading.
3. Why include a design horizon?
A future design year lets you size for expected load growth and panel degradation. That helps avoid undersizing systems for expanding facilities.
4. What is performance ratio?
Performance ratio represents how real system output compares with theoretical output. It reflects inverter efficiency, temperature effects, wiring losses, and other operating realities.
5. Should demand charges be included in savings?
This version uses a simple energy-rate model. Demand-charge savings, time-of-use tariffs, exports, and incentives should be added during financial modeling.
6. Can I use this for carports or ground mounts?
Yes, as a first estimate. Just replace roof area with usable installation area and confirm spacing, orientation, and civil constraints separately.
7. Why does panel count round up?
Solar panels come in whole units. Rounding up ensures the installed capacity meets or slightly exceeds the calculated target instead of falling short.
8. Are the results suitable for procurement?
They are suitable for screening and budgeting, not final procurement. Use a full engineering design before procurement or construction decisions.