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Business solar ROI calculator

Work out the payback, IRR and 25-year cash flow of a solar plant for your business, including the depreciation tax saving and any loan repayments. Enter your own numbers; every assumption is labelled and you can change it.

An estimate from your inputs, not a quote

Your plant
kWp
₹
From your quote, including GST. There is no default: prices vary by site.
kWh/kWp/yr
Assumption: about 1,450 is an estimate for a well-oriented, unshaded roof around Tirupati. Your site survey gives the real figure.
%
Assumption: 0.5% a year. Check the performance warranty on your panel datasheet.
Your electricity
₹/kWh
From your electricity bill.
%
Assumption: 0% keeps tariffs flat, the cautious case. Enter your own view.
%
Assumption: 100% for a site that uses power all day. The rest is exported to the grid.
₹/kWh
Leave blank to value exports at zero. The credit depends on your DISCOM's net-metering or net-billing rules.
Running costs and tax
₹/yr
Cleaning and maintenance. Leave blank if it's in your quote or you'll do it yourself.
%
%
Assumption: 25.17%, the effective rate for many domestic companies on the 22% regime with surcharge and cess. Use your own rate; your tax adviser can confirm it.
Loan (optional)
₹
% a year
years
Use the rate and tenure your lender offers. Loans are subject to lender approval.
Comparing investments
%
Assumption: 10%. Use your own cost of capital.

How it works

  • Generation: size × yearly units per kWp, reduced each year by panel degradation.
  • Bill savings: units used on site × your tariff (rising by the increase you set), plus exported units × their value.
  • Tax saving: depreciation at 40% of written-down value × your tax rate, halved in year 1 if the plant is used for under 180 days that year.
  • Cash flow: year 0 is the cost less any loan; later years are savings plus tax saving, less O&M and loan repayments.
  • Payback is when the cumulative cash turns positive. IRR is the return that makes the 25-year cash flow worth zero today; NPV is its value today at your discount rate.

Before you rely on the numbers

Under the Income-tax Act, 2025, which applies from 1 April 2026, section 33 allows depreciation on written-down value at the rates in Appendix I of the Income-tax Rules, 2026, where solar power generating systems are listed at 40%. If the plant is bought and put to use for less than 180 days in a tax year, that year's allowance is half the rate (section 33(4)). This was the position as of 23 Sep 2026; confirm what applies to your business with your tax adviser. Depreciation applies when you own the plant, not under RESCO.

  • Generation depends on your roof, shade, tilt and dust. A site survey replaces the yield assumption with a figure for your roof.
  • Only your energy charge per unit is saved. Fixed or demand charges on your bill usually stay.
  • Whether exported units earn a credit, and at what rate, depends on your DISCOM's rules and your tariff category.

Comparing buying outright with RESCO? See finance options for business solar, or try our quick CAPEX vs RESCO savings calculator. Already have a quote? We'll compare it line by line, free.