Solar Payback Calculator
Work out rooftop solar payback using net cost after subsidy, degradation, tariff rise, inverter replacement and maintenance, with NPV, IRR and LCOE.
ఇక్కడ ప్రారంభించండి
- ఏమి నమోదు చేయాలి
- ముందుగా సైజింగ్, సబ్సిడీ, బిల్లు ఆదా సాధనాల్లో సామర్థ్యం, టారిఫ్, సబ్సిడీ నిర్ణయించండి; వాపసు కాలం అదే ప్రణాళికను చదువుతుంది.
- ఫలితం అర్థం
- సాధారణ వాపసు కాలం, డిస్కౌంట్ వాపసు కాలం, నికర ప్రస్తుత విలువ, అంతర్గత రాబడి రేటు, యూనిట్ ఖర్చు లభిస్తాయి.
ఉదాహరణ, పరిమితులు చూడండి
- సులభ ఉదాహరణ
- 3 kW, సుమారు ₹1,02,000 నికర ఖర్చు, మొదటి సంవత్సరం ₹31,000 ఆదాతో సాధారణ వాపసు కాలం సుమారు 4–5 సంవత్సరాలు.
- గుర్తుంచుకోండి
- నమూనా సంవత్సరానికి సగం శాతం ఉత్పత్తిని తగ్గిస్తుంది, టారిఫ్ పెంచుతుంది, ఒకసారి ఇన్‌వర్టర్ మారుస్తుంది, ఉచిత కాలం తర్వాత నిర్వహణ జోడిస్తుంది. మూడేళ్లలోపు వాపసు కాలం సాధారణంగా అవాస్తవ టారిఫ్‌ను చూపుతుంది.
మీ ఫలితాన్ని లెక్కించండి
మీ సంఖ్యలు నమోదు చేయండి. మార్చినప్పుడు అంచనా, చార్ట్‌లు నవీకరించబడతాయి.
స్థాపన వాపసు
మీ ప్రణాళిక నుంచి ₹1,02,000 నికర ఖర్చు, ₹31,469 మొదటి సంవత్సరం పొదుపు ఉపయోగించి లెక్కించబడింది.
ఈ నమూనా 25 సంవత్సరాలు నడుస్తుంది; ఉత్పత్తి సంవత్సరానికి సుమారు అర శాతం క్షీణిస్తుంది; ఇన్‌వర్టర్ ఒకసారి భర్తీ అవుతుంది; 8% తో డిస్కౌంట్ చేయబడుతుంది.
Retail tariffs have historically risen by roughly 3–7% a year. A flat tariff is also shown, because the rise is not guaranteed.
- సాధారణ వాపసు కాలం
- 3.4 సంవత్సరాలు
- నికర ఖర్చు ÷ మొదటి సంవత్సరం పొదుపు
- డిస్కౌంటెడ్ వాపసు కాలం
- 4 సంవత్సరాలు
- డబ్బు కాల విలువను లెక్కించిన తర్వాత
- నికర ప్రస్తుత విలువ
- ₹3,75,174
- ధనాత్మకం అంటే పెట్టుబడి డిస్కౌంట్ రేటును దాటుతుంది
- అంతర్గత రాబడి రేటు
- 34.7%
- ఇది భర్తీ చేసే రుణ రేటుతో పోల్చండి
- యూనిట్‌కు ఖర్చు
- ₹2.66
- మీరు ఇప్పుడు యూనిట్‌కు చెల్లించే 8 తో పోలిస్తే
- జీవితకాల పొదుపు
- ₹13.71L
- డిస్కౌంట్ లేకుండా, 25 సంవత్సరాలలో
సంవత్సరాల వారీగా నగదు ప్రవాహం
| సంవత్సరం | ఉత్పత్తి | పొదుపు | నిర్వహణ మరియు భర్తీ | సంచిత |
|---|---|---|---|---|
| 1 | 4,500 | ₹31,469 | ₹0 | -₹70,531 |
| 2 | 4,473 | ₹32,844 | ₹0 | -₹37,687 |
| 3 | 4,446 | ₹34,278 | ₹0 | -₹3,409 |
| 4 | 4,419 | ₹35,774 | ₹0 | ₹32,365 |
| 5 | 4,392 | ₹37,333 | ₹0 | ₹69,698 |
| 6 | 4,365 | ₹38,958 | ₹1,500 | ₹1,07,156 |
| 7 | 4,338 | ₹40,653 | ₹1,500 | ₹1,46,309 |
| 8 | 4,311 | ₹42,420 | ₹1,500 | ₹1,87,230 |
| 9 | 4,284 | ₹44,262 | ₹1,500 | ₹2,29,992 |
| 10 | 4,257 | ₹46,183 | ₹1,500 | ₹2,74,675 |
| 11 | 4,230 | ₹48,184 | ₹1,500 | ₹3,21,359 |
| 12 | 4,203 | ₹50,270 | ₹25,500 | ₹3,46,129 |
| 13 | 4,176 | ₹52,445 | ₹1,500 | ₹3,97,074 |
| 14 | 4,149 | ₹54,711 | ₹1,500 | ₹4,50,285 |
| 15 | 4,122 | ₹57,073 | ₹1,500 | ₹5,05,858 |
| 16 | 4,095 | ₹59,534 | ₹1,500 | ₹5,63,891 |
| 17 | 4,068 | ₹62,098 | ₹1,500 | ₹6,24,490 |
| 18 | 4,041 | ₹64,771 | ₹1,500 | ₹6,87,760 |
| 19 | 4,014 | ₹67,555 | ₹1,500 | ₹7,53,815 |
| 20 | 3,987 | ₹70,455 | ₹1,500 | ₹8,22,770 |
| 21 | 3,960 | ₹73,477 | ₹1,500 | ₹8,94,747 |
| 22 | 3,933 | ₹76,625 | ₹1,500 | ₹9,69,872 |
| 23 | 3,906 | ₹79,904 | ₹1,500 | ₹10,48,276 |
| 24 | 3,879 | ₹83,319 | ₹1,500 | ₹11,30,095 |
| 25 | 3,852 | ₹86,876 | ₹1,500 | ₹12,15,471 |
సాధారణ వాపసు కాలం టారిఫ్ పెరుగుదలను మరియు డబ్బు కాల విలువను పరిగణించదు; 8.0% డిస్కౌంటెడ్ లెక్క మరింత కఠినమైన పరీక్ష.
మీ లెక్కను అర్థం చేసుకోండి
This calculator compares solar's net upfront cost with projected bill savings. Simple payback gives a quick recovery estimate; discounted payback accounts for the time value of money and lifetime costs. NPV, IRR and levelised cost per unit add context. All depend on assumed generation, tariffs, maintenance and equipment life.
Solar Payback Calculator ను ఎలా ఉపయోగించాలి
- 1
Set the size, tariff and subsidy first
Cost after subsidy and the first-year saving come from the shared plan, so confirm those in the sizing, subsidy and bill-savings tools before reading payback.
- 2
Read the simple payback
This is the answer most vendors quote. Note that it ignores tariff rises in your favour and every later cost against you.
- 3
Read the discounted payback and NPV
A discounted payback within the system's life and a positive net present value mean the investment clears the return requirement you set.
- 4
Compare the levelised cost with your tariff
If the solar unit costs less than the grid unit you replace, the case is sound. If it costs more, the tariff or the consumption assumption is the problem.
ఉదాహరణ
Payback on a 3 kW system after subsidy
3 kW installed at ₹1,80,000 with the ₹78,000 central subsidy, saving ₹31,469 in the first year (300 units a month, ₹8 tariff, ₹3 export rate). Maintenance is 3 × ₹500 = ₹1,500 a year from year six, and the inverter replacement is 3 × ₹8,000 = ₹24,000 in year 12. Tariffs rise 5% a year and cash flows are discounted at 8%. Simple payback is ₹1,02,000 ÷ ₹29,969 = 3.4 years; the discounted running total turns positive in year 4 and ends at a net present value of ₹3,75,174.
- Net cost after subsidy
- ₹1,80,000 − ₹78,000 = ₹1,02,000
- First-year saving
- ₹31,469
- Net present value at 8%
- ₹3,75,174
- Internal rate of return
- 34.7%
- Simple payback
- ₹1,02,000 ÷ (₹31,469 − ₹1,500) = 3.4 years
- Discounted payback at 8%
- 4 years
- Lifetime saving, 25 years
- ₹13,71,471 at 5% tariff escalation
- Levelised cost per unit
- ₹2.66
- Present tariff for comparison
- ₹8 per unit in this example
The levelised cost of a solar unit being well below the grid tariff is the real conclusion. Payback is a headline; cost per unit is the comparison that survives inspection.
ఇది ఎలా లెక్కించబడుతుంది
Simple payback is net cost ÷ (first-year saving − annual maintenance), rounded to one decimal. It ignores the time value of money, degradation, tariff rises and the inverter replacement.
The lifetime model runs year by year for 25 years. Output retention is 1 − 0.6% × (year − 1), the saving in year n is first-year saving × retention × (1 + escalation)^(n − 1), maintenance is charged from year six once the five-year free period ends, and one inverter replacement is charged in year 12. On this page, maintenance is ₹500 per kW a year and the inverter replacement is ₹8,000 per kW, the midpoint of the ₹6,000–10,000 range in the config.
Net present value discounts those cash flows at the chosen rate (8% by default): Σ cashflow ÷ (1 + r)^year − net cost. Discounted payback is the first whole year in which the discounted running total turns positive. The internal rate of return is found by bisection as the rate at which net present value reaches zero.
The levelised cost per unit is (net cost + discounted maintenance and replacement) ÷ discounted lifetime generation, with generation at 1,500 units per kW a year before degradation. That's what a solar unit actually costs you, to set against the grid tariff it replaces.
అనుమానాలు మరియు పరిమితులు
- The model runs for 25 years with linear degradation of 0.6% a year, in line with typical module performance warranties.
- Tariff escalation is applied centrally across the lifetime; the historic range is roughly 3% to 7% a year and is not guaranteed.
- One inverter replacement is assumed, with its cost based on inverter capacity. Panel failures under warranty are assumed to be replaced at no cost.
- Maintenance is charged only after the five-year free comprehensive maintenance period, and no insurance, cleaning contract inflation or roof repair is modelled.
- The discount rate is a planning choice. Changing it changes the discounted payback, the net present value and the test the investment has to pass.
తరచుగా అడిగే ప్రశ్నలు
What is a good payback period for rooftop solar in India?
A 4–7-year recovery is only a planning range, not a promise. Tariff, subsidy, system cost and self-consumption drive the result. Check unusually short projections for optimistic generation, export rates or omitted costs.
Why is discounted payback longer than simple payback?
Because the discounted version charges a return requirement on the money tied up and counts later costs. Simple payback treats a rupee saved in year twenty as equal to a rupee saved today, which overstates how quickly the investment recovers.
How long do solar panels last?
Most modules carry a product warranty of around ten to fifteen years and a performance warranty of about twenty-five years. Output declines gradually, typically around half a percent a year, and the model assumes a twenty-five-year horizon with that decline applied.
Which costs appear later in a solar system's life?
The inverter is usually replaced once, somewhere around year twelve, and cleaning, inspection and minor repairs continue after the five-year comprehensive maintenance period that the scheme requires from the vendor. Both are included here.
What discount rate should I use?
A household funding the system from savings or a home-loan-rate loan is reasonable at around 8%. If you are comparing against a specific loan, use that loan's rate so the net present value is measured against the actual alternative.
Does the tariff rise every year?
Not on a fixed schedule, but Indian retail tariffs have historically risen in the low single digits to mid single digits each year. The model uses a central rate and shows the flat-tariff case implicitly through the simple payback, since that one ignores escalation entirely.
Can a payback figure be manipulated?
Yes. High tariffs, full retail credit for exports and omitted maintenance or replacement costs flatter payback. Check every assumption; a low levelised cost alone cannot validate them.