Solar Panel Calculator
Size a rooftop solar system from your electricity bill.
Monthly Electricity Usage
Cost per Unit
Average Peak Sunlight
Installed Cost per kW
Panel Wattage
System Size Required
2.50 kW
Panels Required
7 × 400W panels
Roof Area Needed
16 m²
Estimated System Cost
₹1,37,500
Monthly Savings
₹2,400
Payback Period
4.8 years
CO₂ Offset / Year
2.95 tonnes
How this calculator works
System size is worked out from how much energy you actually use: your monthly usage is converted to a daily average, then divided by your local peak sunlight hours to find the kW capacity needed to cover it. Panel count follows from dividing that capacity by your chosen panel wattage.
Payback period compares the upfront installed cost against the monthly savings from electricity you no longer buy from the grid — it doesn't account for financing costs, subsidies, or panel degradation over time, all of which can shift the real-world payback in either direction.