Congratulations—you’ve installed solar ☀️
The inverter is running. The green light is blinking.
Then your first bi-monthly TNEB bill arrives, and suddenly you’re confused:
- “Why is my bill ₹120 when I generated 500 units?”
- “Where are my banked units?”
- “What are C1, C2, C3 readings?”
Relax.
Here’s a simple, non-technical guide to understanding your TNEB Net Meter bill in 2026.
1. The Three Numbers That Matter Most
Your bi-directional (net) meter tracks electricity like a balance sheet. It records two flows, then calculates one final result.
A. Import – Electricity You Took from TNEB
This is power you pulled from the grid.
When does this happen?
- At night (6 PM–6 AM)
- During cloudy weather
- When AC load is higher than solar generation
Example:
Over 60 days, you imported 400 units.
B. Export – Excess Solar You Gave to TNEB
This is extra solar power that your house didn’t use and sent back to the grid.
⚠️ Important clarification:
This is not your total solar generation.
If your panels produced 600 units:
- 150 units were used instantly by fans, fridge, TV
- Only the remaining 450 units reached the grid
👉 Meter sees only 450 units as “Export”
C. Net Units – What You Actually Pay For
Formula:
Net Units = Import – Export
Example:
- Import: 400 units
- Export: 450 units
Net = –50 units
This single number decides your bill.
2. Understanding “Banked Units”
If Your Net Is Negative (– Units)
Example: –50 units
- Energy charge: ₹0
- Credit: 50 units are banked (carried forward)
Next billing cycle:
If you consume more power (say +30 units), these banked units cancel it out.
You’ll still have 20 units left.
📌 In Tamil Nadu:
- Banked units are valid for one financial year
- Domestic users don’t get cash, only bill adjustment
If Your Net Is Positive (+ Units)
Example:
- Import: 500
- Export: 300
- Net: +200 units
You pay only for 200 units, not 500.
Why This Is Powerful
Without solar:
- 500 units → higher slab → ₹6–₹8/unit
With solar:
- 200 units → lower slab (often free or cheap)
👉 Solar saves twice:
- Fewer units
- Lower tariff slab
3. “My Net Is Zero, Then Why Did I Pay ₹150?”
Good question. Even with zero usage, some charges are mandatory.
Common Fixed Charges
- Fixed Charges (FC):
Based on sanctioned load
Example: ₹50 per kW → 3 kW = ₹150 - Electricity Tax:
Small statutory charge - Network Charges:
Usually zero or minimal for domestic users
⚠️ Warning
If you see Demand Charges or Penalties on a domestic bill, contact your TNEB AE immediately. They shouldn’t be there.
4. What Are C1, C2, C3 Readings?
Some digital meters show time-slot readings, especially for commercial connections.
Typical Time Slots
- C1 (Peak): 6–9 AM & 6–9 PM
- C2 (Day): Normal daytime
- C3 (Off-Peak): 10 PM–5 AM
For domestic consumers, TNEB usually adds them together.
For factories, solar is extremely valuable because it wipes out C2 (expensive daytime units).
5. Common Myths vs Reality
Myth: “All my solar power is sold to TNEB”
Reality: No.
Solar power goes first to your home appliances. Only unused power is exported.
This instant usage is called self-consumption—and it’s the most profitable part of solar.
Myth: “Solar works during power cuts with net meter”
Reality: No.
On-grid inverters shut down during power cuts (anti-islanding) to protect TNEB linemen.
👉 If you want backup during outages, you need a hybrid inverter + battery.
Final Summary (Remember This)
If, on average:
Export > Import
Your bill will usually be only fixed charges
(₹120–₹200 for most homes).
That’s what solar freedom looks like.
Clean power.
Tiny bills.
Full control. ☀️