Solar EPC for Factories in Tamil Nadu: DISCOM Rules, Approvals and Cost

A factory in Tamil Nadu planning 50 kW or more of rooftop solar should plan for net billing, not unit-for-unit net metering. Under the TNERC regulations of 2021, a factory can install up to its sanctioned load or 999 kW, with exports credited at a feed-in tariff and a network charge on every unit generated. At the published band of ₹24,000–32,000 per kW excluding GST, 100 kW costs ₹24–32 lakh.

Which metering route applies to a factory

The Tamil Nadu Electricity Regulatory Commission's Grid Interactive Solar PV Energy Generating System Regulations, 2021 (notified in the Tamil Nadu Government Gazette on 20 October 2021) are the final solar regulations listed on the Commission's website at the time of writing in October 2026. TNERC also issued Generic Tariff Order No. 8 of 2021, and TANGEDCO's technical branch circulated guidelines on it in December 2021. Later tariff orders have revised some charges, so read the table as the 2021 baseline and confirm each figure with the distribution licensee before you commit.

Gross metering needs a separate service line to the nearest HT feeder, laid and maintained at the owner's cost, and the consumer's own supply is billed separately. For most factories whose aim is to cut the electricity bill, net billing is the route, because self-consumed solar units replace units bought at the retail tariff. TANGEDCO's guideline also allows a plant behind the meter that opts for neither route, but only after prior intimation to the licensee.

What the network charge does to your payback

The order levies the network charge on the total units recorded by the generation meter, not only on exports. So each unit your plant makes costs you the network charge, whether you use it or export it. Your saving per self-consumed unit is therefore the retail energy rate on your bill minus the network charge, and each exported unit earns the feed-in tariff minus the same charge. The 2021 feed-in levelised tariffs were ₹3.37 per kWh for 11 to 150 kW and ₹3.10 per kWh for 151 to 999 kW for plants commissioned in the control period then in force, which ran to 31 March 2023. Check what applies to a plant commissioned today.

Run your own bill through the solar calculator, then subtract the network charge from the energy rate before you read the payback. Fixed and demand charges are not reduced by solar in most cases, so use the energy component only.

Capacity, transformer limits and the AC rule

The regulation and TANGEDCO's guideline on the order set these limits.

• AC capacity governs. The plant size is the AC output capacity, reckoned from the demand recorded by the generation meter. DC panels can exceed it, but output above the sanctioned AC capacity is treated as inadvertent injection and is not paid for.
• Transformer cap. The total net-billed solar connected to one distribution transformer should not exceed 90% of its capacity, and gross-metered HT plants should not exceed 70% of the power transformer. The licensee checks this at feasibility.
• Arrears. A consumer with pending dues is not eligible under the regulations, so clear them first.
• Metering. A generation meter with demand recording is required for plants above 10 kW, at the applicant's cost, and the licensee fits a check meter above 20 kW.
• One megawatt. The ceiling is 999 kW, so a plant of 1 MW AC falls outside these routes. Look at captive or open-access options; our open access solar page explains the difference.

Approvals, fees and timelines

LT applications go through the licensee's online rooftop portal. An existing HT consumer applies to the Chief Engineer with the latest HT bill, a project report with layout and single-line diagram, a timeline, proof of ownership of the premises, a no-due certificate and GST details. Registration fees in the regulation run from ₹500 for LT plants up to 20 kW, to ₹5,000 for HT plants above 150 kW and up to 500 kW, and ₹10,000 above 500 kW and below 1 MW.

The regulation sets the licensee's clock. Registration is acknowledged within three working days. Technical feasibility is due within 15 working days of registration, and approval follows within five working days of a positive study. If the system is not feasible, the reason is due within 20 working days. The approval is valid for six months. After you submit the completion report, including a safety certificate from the Chief Electrical Inspector as applicable, the licensee should test and commission within 20 working days and fit the bidirectional meter and synchronise within 10 days after that. Real durations run longer when a transformer needs upgrading or papers are incomplete, so budget a schedule that separates installation from approvals. The electrical inspector approval guide covers the inspection. The state energy agency, TEDA, runs renewable programmes in Tamil Nadu; confirm with the licensee whether any registration with it applies to your category.

What it costs at 100 kW, 500 kW and near 1 MW

Treat these as indicative until a site survey. Tamil Nadu adds its own cost drivers: coastal sites need corrosion-resistant structures and a wind design basis checked for the location, sheet roofs need clamp-fixed rails and a structural check, and a long cable route to the HT panel adds cost. Industrial demand sits in clusters such as Coimbatore, Tiruppur, Hosur, Sriperumbudur and Chennai, where roof area, not the rules, is usually the first constraint.

How Secured Engineers helps

We are a pan-India solar EPC contractor and we mobilise to Tamil Nadu from our offices in Noida (Delhi NCR) and Ludhiana. Design is done in-house, and Fire NOC, CEIG and DISCOM net-metering applications are filed in-house, so the HT application, the single-line diagram and the inspector's file come from one team. Mechanical, electrical, plumbing, fire and solar work can sit under one contract. Our project record lists a 120 kW rooftop plant at Bindal Agencies in Chennai, on a metal-sheet industrial roof shared with turbo ventilators. We have 535+ projects across 18+ states and 89.77% repeat clients.

Send a twelve-month bill, your sanctioned load and a roof photograph, and we will tell you which route fits and what size is realistic. Start from solar EPC for factories, message us on WhatsApp, call +91 70099 85817, or ask for a free proposal.