Free Calculator · 2026

Solar Savings Calculator
for Tamil Nadu Factories (2026)

Electricity is one of the biggest operating costs for factories in Tamil Nadu. Whether you're on TANGEDCO's LT-3, HT-1, or HT-2 tariff slab, this free solar savings calculator shows you exactly how much your factory can save by switching to solar — under a PPA, captive, or group captive model. Enter your monthly EB bill, select your tariff slab and roof area, and get your estimated monthly savings, payback period, and 25-year cumulative returns instantly. Used by industrial buyers across Chennai, Coimbatore, Tirupur, and Salem.

📍 Chennai 📍 Coimbatore 📍 Tirupur 📍 Salem 📍 Madurai
TANGEDCO 2026 tariffs
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Payback & 25-yr ROI
Solar Savings Calculator
Enter your monthly TANGEDCO bill to calculate savings
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Estimates based on TANGEDCO 2026 tariffs & Tamil Nadu solar irradiance (1,400 kWh/kW/year). Actual savings vary by site. Get a free detailed assessment →

How the calculator works

This industrial solar ROI calculator uses four inputs to generate your savings estimate: your monthly TANGEDCO electricity bill, your applicable tariff slab (LT-3, HT-1, or HT-2), your available rooftop or ground area in square feet, and your preferred solar deployment model.

From these, it calculates your recommended system size in kW, the annual units of electricity your plant would generate (based on Tamil Nadu's average irradiance of 1,400 kWh/kW/year), your estimated monthly saving in rupees, and both the payback period and 25-year cumulative return.

1
Enter your EB bill
Your monthly TANGEDCO bill in rupees. This determines your consumption volume and savings baseline.
2
Select tariff slab
LT-3, HT-1, or HT-2. Higher slabs mean faster ROI because the solar cost gap is wider.
3
Enter roof area
Available rooftop or land area caps your maximum system size. Every 100 sq ft supports ~1 kW.
4
Choose your model
PPA requires zero investment. Captive delivers lower per-unit cost. Group captive suits mid-size loads.

What affects your solar savings in Tamil Nadu?

Several factors determine how much a Tamil Nadu factory saves by going solar. Understanding them helps you choose the right structure and set realistic ROI expectations.

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TANGEDCO Tariff Slab
The higher your per-unit grid cost, the wider the gap solar can capture. HT-2 factories at ₹10/unit save significantly more per kWh than LT-3 consumers at ₹7.50/unit.

LT-3: ₹7.50 HT-1: ₹8.50 HT-2: ₹10.00
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Solar Model — PPA vs Captive vs Group Captive
PPA and BOOT models cost ₹3.10–3.30/unit with zero capital outlay — savings from day one. Captive ownership drops your cost to ₹2.40–2.60/unit after the 3–5 year payback, delivering higher long-term returns.
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Roof & Land Area
Your available rooftop or land constrains system size. A 10,000 sq ft roof typically supports 80–100 kW — enough to offset 30–40% of a mid-size factory's consumption.
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BESS (Battery Storage)
Adding battery storage lets your factory use stored solar power during peak evening hours, cutting demand charges and further reducing grid dependency beyond what rooftop solar alone can achieve.
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Solar Irradiance
Tamil Nadu receives among India's highest solar irradiance — 1,350 to 1,500 kWh/kW/year depending on location. Tirupur and Madurai zones outperform Chennai slightly.
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Sanctioned Load & Open Access
Factories above 1 MW sanctioned load qualify for open access tariffs, enabling group captive and third-party PPA structures with even lower per-unit costs and more flexibility.
Related guides from NST Solar
Solar PPA Tariff Guide Group Captive Solar BESS Solutions for Industry Get a Free Site Assessment

Frequently Asked Questions

Common questions from Tamil Nadu industrial buyers about solar savings, payback, and TANGEDCO tariffs.

Most industrial factories in Tamil Nadu save 30–60% on their electricity bill by switching to solar. A factory paying ₹5 lakh/month on TANGEDCO's HT tariff can typically save ₹1.5–2.5 lakh/month under a PPA or captive model, depending on consumption pattern, roof size, and contract structure.
For a captive or group captive solar plant, the typical payback period for Tamil Nadu industries is 3–5 years. Under a PPA or BOOT model, there is no upfront capital investment, so payback is immediate — savings begin from day one of commissioning.
Tamil Nadu industrial consumers fall under LT-3 (commercial, ₹7.50/unit), HT-1 (general industry, ₹8.50/unit), or HT-2 (heavy industry, ₹10.00/unit). Higher tariff slabs produce faster solar ROI because the gap between solar cost and grid cost is wider. You can verify current tariffs on the TANGEDCO official website.
PPA and BOOT models require zero capital investment — ideal for factories that prefer opex over capex. Captive and group captive models require upfront investment but deliver lower per-unit costs (₹2.40–2.60/unit vs ₹3.20 for PPA) and higher long-term savings. The right choice depends on your balance sheet, consumption level, and roof or land availability.
This calculator provides indicative estimates based on current TANGEDCO tariffs, average Tamil Nadu solar irradiance (1,400 units/kW/year), and standard solar model pricing. Actual savings depend on your sanctioned load, open access charges, contract terms, and site-specific conditions. Contact NST Solar for a detailed, site-specific assessment.
Yes. Adding a BESS system allows your factory to store excess daytime solar generation and use it during peak evening hours — reducing grid dependency further and avoiding peak demand charges. NST Solar offers customised BESS solutions integrated with industrial solar plants in Tamil Nadu.
Any industrial unit paying more than ₹1 lakh/month on TANGEDCO electricity typically qualifies for a viable solar PPA. For captive and group captive models, factories consuming above 10 lakh units/year see the strongest ROI. Our calculator works for bills from ₹1 lakh to ₹50 lakh/month.
Ready to see your exact savings?

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Last updated: May 2026 · Tariff data: TANGEDCO 2025–26 · Irradiance data: MNRE Solar Atlas · Published by NST Global Solar & Wind Energy Pvt Ltd, Chennai
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