Quick answer: Enter your monthly TANGEDCO bill and available roof area below to instantly see your recommended solar system size, applicable PM Surya Ghar subsidy, net cost, payback period, and 25-year lifetime savings. Most Chennai homes recover their investment in 3–6 years and then generate free electricity for 20+ more.
Lifetime savings (25 years)
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Year 25 bill (no solar): –
Tariff rise: 6%/yr
Recommended size: –
System cost
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Govt. subsidy
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Your net cost
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Payback
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Estimates only, based on typical Chennai sun hours, TANGEDCO tariffs, and a 6%/yr tariff escalation assumption. System cost varies by panel brand/type. Actual figures depend on your site survey and chosen equipment.
How This Solar Calculator Works
The calculator uses your monthly electricity bill to estimate your household’s energy consumption, then recommends a real, sellable system size (in whole kW increments) that would offset most of that usage — cross-checked against how much your available roof area can physically support (roughly 100 sq ft per kW). It applies the current PM Surya Ghar Muft Bijli Yojana subsidy slabs for residential systems, and projects 25-year savings assuming TANGEDCO tariffs rise about 6% per year, which is how utility costs have historically trended.
What Is the PM Surya Ghar Subsidy?
PM Surya Ghar Muft Bijli Yojana is the Government of India’s rooftop solar subsidy scheme, offering up to ₹78,000 for residential systems (3 kW and above), on a sliding scale for smaller systems. It doesn’t apply to commercial installations. Read our full Tamil Nadu guide to the subsidy →
Frequently Asked Questions
How accurate is this solar calculator?
It gives a reliable ballpark based on typical Chennai conditions and average TANGEDCO tariffs. Actual system size, cost, and savings depend on your roof’s shading, orientation, and a proper site survey — which we offer free.
What roof area do I need for a 3 kW solar system?
Roughly 300 sq ft of unshaded roof space, using the standard estimate of about 100 sq ft per kW.
How is the payback period calculated?
Payback period is your estimated net system cost (after subsidy) divided by your current annual electricity bill. Most Chennai residential systems pay back in 3–6 years.
Why does the 25-year savings figure assume rising tariffs?
Electricity tariffs in Tamil Nadu have historically increased over time. Projecting a flat, unchanging bill for 25 years would understate your real savings, so the calculator assumes a 6%/year rise — the same assumption used industry-wide for long-term solar ROI projections.
Does the subsidy apply to commercial solar installations?
No — the PM Surya Ghar subsidy is for residential rooftop solar only. Commercial and business installations follow separate depreciation and financing benefits; see our Commercial Solar page for details.
Is this calculator specific to Chennai?
Yes — the sun-hour and generation assumptions are calibrated for Chennai’s climate and TANGEDCO’s tariff structure.
Want an exact quote instead of an estimate? Send us your TANGEDCO bill on WhatsApp for a free, no-obligation site visit and quote.