Solar Rooftop Calculator
Estimate your rooftop solar system size, PM Surya Ghar subsidy, net cost, savings and payback.
Built & reviewed by Ankit Madia, Founder & Markets Trader
Rooftop Solar Calculator
This calculator turns your electricity bill into a recommended rooftop solar system size, then works out the cost after the government subsidy, the roof area required, and how quickly the investment pays for itself. It is built for Indian homes on the PM Surya Ghar scheme with net metering.
How the System Size Is Worked Out
Monthly units = Bill / Tariff
System size (kW) = Monthly units / 30 / Generation per kW
Roof area = System size × 100 sqft
One kilowatt of panels generates about 4 units a day on average across India, though this ranges from roughly 3.5 units in cloudier regions to over 5 in sunny states like Rajasthan and Gujarat. You can adjust the generation figure to match your location.
PM Surya Ghar Subsidy Slabs
| System Size | Central Subsidy |
|---|---|
| 1 kW | ₹30,000 |
| 2 kW | ₹60,000 |
| 3 kW and above | ₹78,000 (maximum) |
Some states add their own top-up subsidy, so your net cost may be lower than shown here.
Why Rooftop Solar Makes Sense
- After subsidy, payback is typically 3 to 5 years.
- Panels are warranted for 25 years, giving two decades of nearly free power.
- Net metering credits the surplus you export to the grid.
- Electricity tariffs keep rising, so your savings grow over time.
Things This Estimate Does Not Include
For simplicity, the payback and 25-year savings assume a flat tariff and steady generation. In reality panels lose about 0.5% output per year while tariffs usually climb faster than that, so real savings tend to be higher. Always get a site survey and quotes from empanelled vendors before deciding.