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Solar Size & Payback Calculator
Payback the way net billing actually pays it: the units you use yourself are worth the bill they remove; the units you export are worth Rs 8.13. Everything else is a brochure.
The honest headline: for a typical home on a Rs 18,000 – 30,000 bill, payback under net billing runs about 3 to 5 years — and the biggest lever is not the panel price, it is the share of production your home uses while the sun is up.
Size a system and price the payback — honestly
Or leave blank and give the bill amount instead.
Planning range for 5 kW on-grid: Rs 7 – 9.5 lakh for a 5 kW on-grid system (installer listings, October – November 2026) — a planning range, not a quote.
The share of what your panels produce that your home uses directly. 55% is a stated assumption used by the most careful published estimates — a home empty all day is lower; a home running daytime loads is higher. This one input moves the answer more than any other.
Planning assumption: one kW of panels produces about 120 units in an average month. Your roof, city and season move this — edit it.
Exported units earn this — not the retail rate. New connections are net billing since 9 February 2026 (S.R.O. 251(I)/2026).
System size is capped at your sanctioned load under the regulations.
Why the old payback stories no longer apply
Before February 2026, exported units offset imported units one-for-one, so every produced unit was worth the retail rate and payback stories of two years were common. Net billing ended that: exports now earn the average energy purchase price. Pages still selling the 1:1 story — some of them untouched since the old regime — overstate returns exactly the way a telescopic bill calculator understates bills: a wrong method under fresh-looking numbers. If you already own a system, check your own bill with the net billing calculator; if you are deciding, the is-solar-worth-it guide works through the decision in order.
Questions
How long does solar take to pay for itself now?
For a daytime-occupied home with a bill in the Rs 18,000 – 30,000 range, published estimates under net billing cluster around 3 to 5 years — driven mostly by how much of the production the home uses directly. This calculator shows its working: change the self-consumption share and watch the payback move. Any estimate that values exported units at the retail rate is using the repealed rules and will promise a payback the new regime cannot deliver.
Why does self-consumption matter so much?
A unit you produce and use yourself removes a unit billed at retail — Rs 33 to Rs 60 or more once the fixed charge, adjustments and GST are counted. A unit you export earns the export rate, Rs 8.13 by the current sourced default. Same panel, same sunshine, four times the value — so daytime loads are worth more than a bigger system.
What size system do I need?
Roughly: your monthly units divided by about 120 units per kW per month, rounded to a standard size — and capped at your sanctioned load under the regulations. Oversizing past your daytime use mostly earns the export rate, which stretches the payback. The calculator recommends a size from your usage and shows the split.
Is the system cost here a quote?
No. The Rs 7 – 9.5 lakh range for a 5 kW on-grid system is a planning range from current installer listings, shown so the payback has an honest denominator. Your roof, structure and inverter choice move the real figure — get quotes, then bring the number back here.