Calculator Inputs
Example Data Table
| Scenario | Monthly Usage | Panel Wattage | Sun Hours | Target Offset | Panels Needed | Estimated Output |
|---|---|---|---|---|---|---|
| Urban Home | 700 kWh | 540 W | 5.2 | 90% | 9 | 659 kWh/month |
| Family Villa | 1200 kWh | 550 W | 5.6 | 100% | 15 | 1247 kWh/month |
| Small Office | 1800 kWh | 600 W | 5.8 | 85% | 18 | 1566 kWh/month |
Formula Used
The calculator sizes a solar array using usage, target offset, sun hours, module size, and real-world losses. It also estimates savings from self-consumed and exported electricity.
Combined losses include shading, soiling, mismatch, and temperature adjustments. This gives a more realistic production estimate than using nameplate wattage alone.
How to Use This Calculator
- Enter your average monthly electricity usage from recent utility bills.
- Choose the percentage of usage you want your solar system to offset.
- Provide panel wattage, sun hours, and expected system performance.
- Add tariffs, roof area, inverter size, and cost assumptions.
- Include realistic loss percentages for shading, dust, mismatch, and heat.
- Press the calculate button to view required panels and savings above the form.
- Export the summary as CSV or PDF for proposals, budgeting, or comparisons.
Why These Results Matter
This calculator helps compare design goals against physical roof space, inverter sizing, export credit assumptions, and long-term savings. It is useful for homeowners, installers, and energy consultants preparing preliminary solar plans.
Frequently Asked Questions
1. What does net metering mean?
Net metering lets your solar system send excess electricity to the grid. Your utility then gives bill credits based on exported energy under its program rules.
2. Why are sun hours important?
Sun hours convert panel wattage into expected energy production. Higher average sun hours generally reduce the number of panels needed for the same target offset.
3. Why is self consumption separate from exports?
Self-consumed solar offsets imported electricity at the retail rate. Exported power often earns a different credit rate, so separating both gives more realistic savings.
4. What is a good performance ratio?
Many rooftop systems use a base performance ratio around 75% to 85%. Final values depend on wiring quality, temperature, dust, shading, and equipment selection.
5. Can roof area limit the project?
Yes. Even if energy needs suggest more modules, available roof space may cap the final design. This tool checks whether estimated roof capacity can fit the requirement.
6. Why does the calculator show DC and AC sizes?
Panels are rated in DC, while inverters are rated in AC. Comparing both gives the DC/AC ratio, which helps evaluate clipping risk and inverter loading.
7. Is payback the same as profit?
No. Simple payback only estimates how long savings take to recover upfront cost. It does not include financing, maintenance, inflation, taxes, or replacement costs.