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Solar ROI Calculator India

Enter your electricity bill and state to see the rooftop system you need, your PM Surya Ghar subsidy, payback period and 25-year return.

Updated · By Niraj Kumar · 1 source

Your home

Solar forSolar for
From your bill, enterFrom your bill, enter
₹
₹100₹50K

About 253 units a month on the MSEDCL tariff. Use a year's average if your bill swings with the seasons.

Roof typeRoof type

Fine-tune

kW

Sized to cover a year of your consumption, at 5.4 peak sun hours a day in Maharashtra.

sq ft

About 100 sq ft per kW. Leave at 0 for no limit.

₹

Typical for an on-grid system from an empanelled vendor. Replace it with your quote.

%
0%15%

Indian residential tariffs have historically risen 4-7% a year.

%
0%2%

Monocrystalline panels typically lose about 0.5% a year.

How you payHow you pay
Pays for itself in1.7 yearsthen ₹14.67 L ahead after 25 years

A 2 kW system makes about 253 units a month, 100% of your use. Your bill drops from ₹3,000 to about ₹151 in year one.

Installed cost
₹1,20,000
PM Surya Ghar subsidy
− ₹60,000
Net cost to you
₹60,000
Saving in year one
₹34,144
Return (IRR)
61.4% a year
over 25 years, before tax
CO₂ avoided
51 tonnes
over 25 years
Subsidy50%
  • You pay50%
  • Central subsidy50%
Your money over 25 yearsStill to recoverAhead
₹-5 L₹0₹5 L₹10 L₹15 LPayback, year 1.704812162025
Year-by-year cash flowShow
YearUnits madeBills without solarBills with solarUpkeep and EMIsRunning total
13,035₹35,958₹1,814₹0-₹25,856
23,020₹37,756₹2,007₹0₹9,893
33,005₹39,644₹2,215₹0₹47,322
42,990₹41,626₹2,438₹0₹86,510
52,975₹43,707₹2,677₹0₹1,27,540
62,960₹45,893₹2,933₹1,200₹1,69,299
72,945₹48,187₹3,208₹1,200₹2,13,079
82,931₹50,597₹3,502₹1,200₹2,58,973
92,916₹53,127₹3,817₹1,200₹3,07,083
102,901₹55,783₹4,154₹1,200₹3,57,512
112,887₹58,572₹4,514₹1,200₹4,10,371
122,873₹61,501₹4,898₹15,200₹4,51,773
132,858₹64,576₹5,310₹1,200₹5,09,839
142,844₹67,804₹5,749₹1,200₹5,70,694
152,830₹71,195₹6,218₹1,200₹6,34,471
162,815₹74,754₹6,719₹1,200₹7,01,306
172,801₹78,492₹7,253₹1,200₹7,71,346
182,787₹82,417₹7,822₹1,200₹8,44,740
192,773₹86,538₹8,430₹1,200₹9,21,647
202,760₹90,864₹9,078₹1,200₹10,02,234
212,746₹95,408₹9,767₹1,200₹10,86,674
222,732₹1,00,178₹10,503₹1,200₹11,75,150
232,718₹1,05,187₹11,285₹1,200₹12,67,851
242,705₹1,10,446₹12,119₹1,200₹13,64,979
252,691₹1,15,969₹13,006₹1,200₹14,66,741

How the Solar ROI Calculator India works

The bill you enter is worked backwards through your DISCOM's slabs, fixed charges, surcharges and duty to the units you use. The panels' yearly output is set against that use under net metering, and each month is re-billed on what is left. Because the units solar removes come off your most expensive slab first, the saving per unit is often well above the average rate on your bill. Tariffs rise by the escalation rate each year while the panels slowly lose output; maintenance, an inverter replacement in year 12 and any loan repayments are taken off, and the running total gives the payback year.

Saving₍y₎ = [Bill(U) − Bill(U − G₍y₎/12)] × 12 × (1 + e)^(y−1), G₍y₎ = kW × H × 365 × PR × (1 − d)^(y−1)
U
Units you use a month, worked out from your bill
G₍y₎
Units the panels make in year y
H
Peak sun hours a day in your state
PR
Performance ratio: the share of rated output that reaches the meter, 0.77 here
e
Yearly rise in electricity prices
d
Yearly loss in panel output

Worked example

A Pune home on MSEDCL with a ₹3,000 monthly bill and a flat RCC roof, assuming prices rise 5% a year.

  1. 1Working the bill back through the MSEDCL slabs, charges and duty gives about 253 units a month
  2. 2At 5.4 peak sun hours, 2 kW makes about 253 units a month, 100% of that use
  3. 32 kW at ₹60,000 per kW costs ₹1,20,000; PM Surya Ghar pays ₹60,000, leaving ₹60,000
  4. 4The first year saves ₹34,144, and the saving grows as tariffs rise

The system pays for itself in about 1.7 years and leaves the household about ₹14,66,741 ahead over 25 years.

Frequently asked questions

What size of solar system do I need?

Enough to cover a year of your consumption. A kW of panels makes about 4 units a day in most of India, 110-130 a month, so a home using 300 units a month needs about 2.5 kW. The calculator works your units out from your bill using your DISCOM's own slabs, then sizes the system to your state's sunshine.

What is a realistic payback period for rooftop solar in India?

With the PM Surya Ghar subsidy, most homes paying ₹2,000 or more a month recover the cost in 2-5 years. It is fastest where tariffs are steep, such as Maharashtra's upper slabs, or where the state adds its own subsidy, and slowest on cheap flat tariffs. Panels then keep producing for 25 years or more.

Does the calculator account for rising electricity prices?

Yes. Residential tariffs have historically risen 4-7% a year, and every year's saving is scaled up by the rate you choose, 5% by default. Panel output is scaled down by 0.5% a year for degradation, and maintenance after the five-year vendor contract and an inverter replacement in year 12 are both deducted.

Can a housing society or RWA use this?

Yes. Societies get ₹18,000 per kW of the central subsidy for common facilities, up to 500 kW and 3 kW a house, and no state top-up. The housing society solar calculator applies that subsidy to the common-area bill and splits the cost and saving per flat.

How much is the PM Surya Ghar subsidy?

₹30,000 per kW for the first 2 kW and ₹18,000 for the third, so ₹30,000 for 1 kW, ₹60,000 for 2 kW and ₹78,000 for 3 kW or more. It is paid into your bank account after the DISCOM inspects and commissions the system, and only for installations by an empanelled vendor using ALMM-listed panels, applied for through pmsuryaghar.gov.in.

Why is my saving per unit higher than my average rate?

Residential tariffs are telescopic: the first units are cheap and each slab above costs more. Solar takes units off the top of your bill, so it removes the dearest ones first. A home in a ₹10-plus slab saves that rate on every unit the panels cover, even if the bill averages out lower.

Why not simply fit the biggest system my roof will hold?

The central subsidy stops rising at 3 kW, and under net metering surplus units are usually bought back at the regulator's average power purchase cost, often ₹2-3 a unit, far below what you pay for grid power. Sizing to your own consumption earns the full retail rate on every unit. The calculator suggests that size; override it to see what a bigger system does to the return.

Sources

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