Calculator Inputs
Use the form below to estimate array size, battery storage, inverter rating, charge controller current, panel count, and expected annual output.
Example Data Table
| Scenario | Daily Load | Peak Sun Hours | Array Size | Panels | Battery | Inverter |
|---|---|---|---|---|---|---|
| Small home hybrid | 12 kWh/day | 5.2 | 3.48 kW | 7 × 500W | 22.50 kWh | 3000 W |
| Medium villa backup | 22 kWh/day | 5.8 | 5.50 kW | 10 × 550W | 41.25 kWh | 5000 W |
| Off-grid workshop | 35 kWh/day | 6.0 | 8.40 kW | 16 × 550W | 75.47 kWh | 9000 W |
Formula Used
Design Daily Load = Daily Energy Use × (1 + Design Margin)
Overall Derate = (1 − System Losses) × Inverter Efficiency × Controller Efficiency
Required PV Array (kW) = Design Daily Load ÷ (Peak Sun Hours × Overall Derate)
Number of Panels = Ceiling[(Required PV Array × 1000) ÷ Panel Wattage]
Battery Capacity (kWh) = (Design Daily Load × Autonomy Days) ÷ Depth of Discharge
Recommended Inverter = Peak Load × (1 + Surge Margin)
Charge Controller Current = Actual Array Watts ÷ Battery Voltage
How to Use This Calculator
- Choose the solar system type.
- Enter your average daily electricity use in kWh.
- Enter the highest simultaneous load in watts.
- Add site peak sun hours from your solar resource estimate.
- Set realistic system losses, inverter efficiency, and controller efficiency.
- Enter design margin and surge margin for reserve capacity.
- Provide battery autonomy days, depth of discharge, and battery voltage.
- Enter the panel wattage and panel area.
- Optionally enter roof area to check whether the array fits.
- Press the calculate button to view results, chart, and export options.
Frequently Asked Questions
1. What does peak sun hours mean?
Peak sun hours convert variable sunlight into equivalent full-power hours. A site with 5.5 peak sun hours receives the same daily energy as 5.5 hours of ideal full irradiance.
2. Why are system losses important in solar sizing?
Real systems lose energy through heat, wiring, inverter conversion, dirt, shading, and mismatch. Ignoring losses makes the array look smaller than what is actually needed in operation.
3. How is battery autonomy used here?
Autonomy days represent how long the battery should support loads when solar production is weak. More autonomy increases battery capacity and cost, but improves resilience.
4. What is depth of discharge?
Depth of discharge is the share of stored energy you allow the battery to use. Lower allowable discharge means a larger nominal battery bank is needed.
5. Why does the calculator ask for peak load?
Daily energy sizes the array, but peak load sizes the inverter. A system can have low daily use and still need a larger inverter because several devices run together.
6. Can I use this for grid-tied systems?
Yes. Grid-tied users can still size the array and inverter. Battery outputs become more useful when backup storage is part of the project.
7. Does roof area alone confirm panel fit?
No. Roof fit also depends on orientation, setbacks, tilt frames, obstructions, and walkways. The area check is a quick planning estimate, not a final layout study.
8. Why is there a monthly graph?
Monthly plotting helps compare estimated generation with demand across the year. It highlights seasonal gaps that may justify more panels, storage, or load shifting.