Solar savings calculator
Enter your system size, tariff and sun hours to see annual savings, the payback period and the simple 25-year saving — with the central subsidy applied.
| Breakdown | Value |
|---|
Estimate. The method and sources are on this page — check them against your own case before you act.
How it is calculated
A solar saving is the value of the units you no longer buy from the discom. The payback period is the net cost of the system divided by that yearly saving.
Annual units = kW × sun hours × 365 × performance ratio · Annual saving = units × tariff · Payback = (installed cost − subsidy) ÷ annual saving
Estimate yearly generation
A 3 kW system in a place with 4.5 peak sun hours and a 0.75 performance ratio generates about 3 × 4.5 × 365 × 0.75 ≈ 3,696 units a year.
Value those units at your tariff
At ₹8 a unit that is about ₹29,565 a year. If your slab rate is ₹6.50, the saving drops to roughly ₹24,000 — which is why the tariff is an input.
Remove the subsidy, then divide
A 3 kW system at ₹50,000/kW costs ₹1,50,000; after the ₹78,000 central subsidy the net is ₹72,000. Dividing by the annual saving gives a payback of about 2.4 years.
Assumptions behind the savings result
| Item | Default used | Where to get your value |
|---|---|---|
| Electricity tariff | ₹8.00 per unit (editable) | Your latest electricity bill — total bill ÷ units consumed. |
| Peak sun hours | 4.5 hours a day (editable) | Local solar installer estimate or a solar resource map for your district. |
| Performance ratio | 0.75 (selectable) | 0.70 for dusty or older systems, 0.80 for clean and well-ventilated panels. |
| Central subsidy | ₹30,000/kW first 2 kW, ₹18,000 third kW | Pulled automatically from the PM Surya Ghar slabs. |
| Installed cost | ₹50,000 per kW (editable) | MNRE benchmark; replace with your installer's quote. |
| 25-year savings | Annual saving × 25, no escalation | A simple figure that ignores tariff increases and panel degradation. |
| Unit | 1 unit = 1 kWh | The same unit your discom bills you for. |
What most pages get wrong
Your slab decides the saving
Two homes with the same panels save different amounts because one pays ₹6 a unit and the other ₹9. Always recalculate with your own bill's rate.
Most Indian rooftops pay back in 3 to 5 years
With a subsidy and a tariff above ₹7, a clean 3 kW system usually recovers its cost within four years — but the number moves with sun hours, tariff and price.
Panels outlive the payback several times over
A rooftop system is typically expected to produce for about 25 years. The simple 25-year figure multiplies one year's saving without assuming a tariff rise, so it is a floor, not a forecast.
A unit is a kWh
Every unit your meter records is one kilowatt-hour. Generated and consumed units are valued the same way at your retail tariff.
Frequently asked questions
How much does a 3 kW solar system save per year?+
What is the payback period for rooftop solar in India?+
Should I use my average tariff or the highest slab?+
Does the calculator include panel degradation?+
Why does the calculator use 4.5 sun hours?+
Is the saving the same as my bill going to zero?+
Sources, dates and a changelog.
Every number this calculator uses is either an input you control or a value from the sources below. The formula is compiled and tested at build time, so the page cannot ship with a broken calculation.
Sources
This page
- Last verified: 29 October 2026
- Next review: 29 April 2027
- Vertical: Solar & Energy
- Build tests: 3 passed
- Changelog: 1 entry
How we handle errors
- Spotted a mistake? Report it — we correct and log it.
- Corrections appear in the changelog below.
- Read the methodology and the disclaimer.