Rooftop solar in Tamil Nadu is governed by a mix of central and state rules — the PM Surya Ghar scheme sets the subsidy, but TANGEDCO and the Tamil Nadu Electricity Regulatory Commission (TNERC) set the actual technical and billing rules that determine how your system connects to the grid and how your savings are calculated. This guide breaks down what actually matters, in plain language.
Who Regulates What
TNERC
The Tamil Nadu Electricity Regulatory Commission sets the net metering regulations and tariff orders that govern how solar export is credited and paid across the state.
TANGEDCO
The state distribution licensee that implements TNERC's rules on the ground — processing your application, installing the net meter, and issuing your electricity bill.
TEDA
The Tamil Nadu Energy Development Agency, the state's nodal agency coordinating renewable energy schemes, including subsidy implementation alongside the central PM Surya Ghar programme.
Net Metering: The Core Rule You Need to Understand
Net metering is the billing arrangement that makes rooftop solar financially worthwhile. A standard electricity meter only counts what you draw from the grid — it can't handle power flowing the other way. A bi-directional net meter tracks both what you import from TANGEDCO and what you export back to the grid when your panels produce more than your home is using. At each billing cycle, the difference between what you imported and exported determines your bill; unused export credits typically carry forward, with any remaining surplus settled at an annual reconciliation.
System Size Limits
| Consumer Category | Typical Net Metering Limit |
|---|---|
| Residential (domestic) | Up to 10 kW |
| Commercial / LT industrial | Up to 500 kW |
A key underlying rule across categories: your solar system's capacity should not exceed your connection's sanctioned electrical load. This is checked during the feasibility review, which is one more reason a proper site survey and TANGEDCO liaison matters before you commit to a system size.
The Application Process, Simplified
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Apply via the Unified Solar Rooftop Portal (USRP)
Tamil Nadu processes rooftop solar net-metering applications through TANGEDCO's USRP portal, which also connects with the central PM Surya Ghar portal for subsidy coordination.
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Feasibility Review
TANGEDCO checks your proposed system against your sanctioned load and site conditions before approving installation.
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Installation & Documentation Submission
Your installer submits the system's technical details — including the single-line diagram (SLD) and equipment certification — as part of the application.
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Net Meter Installation & Inspection
TANGEDCO installs the bi-directional net meter and conducts a final inspection before your system is allowed to export power to the grid.
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Commissioning
Once inspection is complete, your system is officially commissioned and begins operating under net metering.
Processing timelines commonly run in the range of 30 to 60 days from application to commissioning, though this varies with documentation quality and current processing volumes — a good installer who handles this liaison directly tends to move faster than a self-managed application.
Documents Typically Required
- TANGEDCO electricity service connection number
- Recent electricity bill
- Single-line diagram (SLD) of the proposed solar system
- Inverter and panel certification (IEC/BIS compliance as applicable)
- Proof of installer's MNRE empanelment
- GST invoice for the installation
How Your Solar Export Is Paid or Credited
Surplus power you export to the grid is credited against your consumption, generally at a buyback rate set by TNERC that is lower than the retail tariff you'd otherwise pay. This rate is periodically revised by TNERC tariff orders, so treat any specific per-unit figure you see online as indicative and confirm the current rate directly with TANGEDCO or your installer before finalizing your savings expectations.
The Free 100-Units Rule — and Why It Matters for Solar
Tamil Nadu provides the first 100 units of electricity free each month to domestic consumers, but only if your total monthly consumption stays at or below 100 units. Cross that threshold, and all units in that billing period are charged at the applicable slab rate — the free benefit doesn't apply partially.
What this means practically: households consuming meaningfully more than 100 units a month (a common pattern for homes running air conditioning, especially through Chennai's summer) see the most financial benefit from solar, since they're already paying full slab rates on their consumption. Very low-consumption households should factor this in when estimating payback, since their starting bill may already be minimal.
Tamil Nadu's new state top-up subsidy: In the August 2026 state budget, the Tamil Nadu government announced an additional state-level rooftop solar subsidy of up to ₹22,000 for domestic consumers, layered on top of the central PM Surya Ghar subsidy. Combined, eligible households could receive up to approximately ₹1 lakh in total subsidy for systems above 3kW. The state has earmarked ₹50 crore for the scheme, described as operating in convergence with PM Surya Ghar. Detailed implementation guidelines for how the two subsidies combine were still being finalized at the time of this announcement — confirm current status and eligibility with your installer or through TEDA before assuming the full combined amount applies to your specific application.
Compliance Basics Worth Knowing
- Equipment must meet applicable BIS/IEC technical standards for panels and inverters
- Proper earthing and lightning protection are standard technical requirements for grid-connected systems, not optional extras
- Your installer should be MNRE-empanelled for the smoothest application processing
- Any modification to an already-commissioned system (like adding capacity later) generally requires a fresh feasibility check with TANGEDCO, not just a self-managed upgrade
Frequently Asked Questions
What is the maximum solar system size allowed under TANGEDCO net metering?
Residential rooftop systems are generally eligible for net metering up to 10 kW, while commercial and LT (low-tension) industrial consumers can go up to 500 kW, subject to your sanctioned electrical load. Your solar system's capacity should not exceed your connection's sanctioned load, so this is worth confirming during your site survey.
Who regulates rooftop solar rules in Tamil Nadu — TANGEDCO or TNERC?
The Tamil Nadu Electricity Regulatory Commission (TNERC) sets the net metering regulations and tariff orders, while TANGEDCO, as the state distribution licensee, implements them — processing applications, installing net meters, and billing consumers. TEDA (Tamil Nadu Energy Development Agency) is the state nodal agency coordinating subsidy schemes.
How does Tamil Nadu's free 100-units electricity policy affect solar savings?
Tamil Nadu gives domestic consumers their first 100 units free each month, but only if total consumption stays at or below 100 units — if you exceed it, all units are billed at the applicable slab rate and the free benefit no longer applies. This means solar delivers the most savings for households consuming meaningfully above 100 units per month, since low-consumption households already pay little or nothing before solar.
Is there a Tamil Nadu state subsidy on top of the central PM Surya Ghar subsidy?
Yes. In the August 2026 state budget, the Tamil Nadu government announced an additional state top-up subsidy of up to ₹22,000 for domestic rooftop solar, layered on top of the central PM Surya Ghar subsidy of up to ₹78,000 — bringing the combined maximum benefit to around ₹1 lakh per eligible household. Implementation guidelines for combining the two were still being finalized at the time of this announcement, so confirm current status with your installer or TEDA before assuming the full amount applies to your application.
Want help navigating TANGEDCO's approval process and the latest subsidy stacking rules? Talk to Arka Solar Energy for a free consultation — no obligation.