Net metering is the part of going solar that has nothing to do with panels or inverters — it's paperwork with TANGEDCO. Get it right and it's mostly invisible; get it wrong and it's the single biggest source of delay in a Chennai rooftop solar install. Here's exactly how it works.
What net metering actually does
Under TANGEDCO's setup, your solar panels don't power your home directly. Every unit they generate is exported to the grid, tracked by a bidirectional meter installed as part of the process. Your home, in turn, draws all its power from the grid as normal — exactly as it did before solar.
At the end of each billing cycle, TANGEDCO nets your total exported units against your total imported units. If you exported more than you imported, the surplus becomes a credit on your account, valid for 365 days before it expires. If you imported more than you exported, you're billed for that shortfall in the usual bimonthly cycle. That's what "net" metering means — your bill or credit reflects the difference between the two totals over the cycle, not what you generated and consumed at any single moment.
The step-by-step process
- Site survey and system design (1–2 days). An engineer assesses your roof — orientation, shading, structural load, available area — and sizes a system against your actual consumption pattern.
- Net metering application to TANGEDCO. Your EPC contractor files the application on your behalf through TANGEDCO's portal, along with the required documents (below). This is normally where delays creep in if paperwork is incomplete.
- Technical feasibility approval. TANGEDCO reviews the application against local transformer/feeder capacity and issues feasibility approval.
- Installation. Once approved, the physical installation — mounting structure, panels, inverter, wiring — typically takes 1–2 days for a residential system.
- Inspection by TANGEDCO. A TANGEDCO officer inspects the completed installation for compliance with safety and technical standards.
- Bidirectional meter installation. TANGEDCO installs (or reconfigures) the meter that separately tracks import and export.
- Commissioning and Power Purchase Agreement. Once the meter is live, your system is officially commissioned and a net metering agreement is signed.
Documents you'll need
- Latest TANGEDCO electricity bill (your 10-digit consumer/service number)
- Proof of property ownership or a No-Objection Certificate if rented
- Identity proof of the connection holder
- Signed technical drawings and single-line diagram of the proposed system (prepared by your EPC contractor)
- Net metering application form (filed through TANGEDCO's portal)
A properly run EPC contractor handles the drawings and portal filing directly — you're mainly needed for signatures and the bill/ID copies.
How your bill is calculated after net metering
TANGEDCO's domestic (LT-1) tariff is slab-based and billed bimonthly. The rate you pay depends on your total bimonthly consumption band — and once you cross into a higher band, that higher rate applies to more of your usage, not just the units above the threshold. That's what makes solar most valuable for households in the higher slabs.
| Bimonthly units | Rate structure |
|---|---|
| 1 – 100 | Free |
| 101 – 200 (if total ≤ 500) | ₹2.35 / unit |
| 201 – 400 | ₹4.70 / unit |
| 401 – 500 | ₹6.30 / unit |
| 501 – 600 (if total > 500) | ₹8.40 / unit |
| 601 – 800 | ₹9.45 / unit |
| 801 – 1,000 | ₹10.50 / unit |
| Above 1,000 | ₹11.55 / unit |
With net metering, your exported solar units offset your imported units before this slab structure is applied to what's left — so a well-sized system doesn't just save you the per-unit rate, it can keep you out of the higher slabs entirely. This is the exact slab logic our savings calculator uses to estimate your bill.
Common reasons applications get delayed
- Consumer number or connection name mismatch with the bill on file
- Incomplete or incorrectly formatted single-line diagrams
- Property ownership documentation not matching the application
- Local transformer capacity constraints requiring additional TANGEDCO review
Most of these are avoidable simply by having an experienced EPC contractor prepare the filing rather than doing it yourself — this is the single highest-leverage thing you can do to keep your timeline to the shorter end of 4–8 weeks.
Want your exact numbers instead of general slabs?
Share your TANGEDCO consumer number and our calculator will estimate your actual usage and system size.