5 peak sun hours
Rooftop solar in Tamil Nadu
Tamil Nadu operates net billing with a feed-in rate of ₹2.8 per unit . Net billing — exported units are bought at a lower feed-in rate
Peak sun hours5 h
1 kW generates3.9 units/day
Effective tariff at 300 units₹3.73
Fixed charge₹40
Domestic tariff slabs
| Slab (units) | Rate per unit | Fixed charge |
|---|---|---|
| 0 – 100 | ₹0 | ₹40 |
| 100 – 200 | ₹4.6 | ₹40 |
| 200 – 400 | ₹6.6 | ₹60 |
| 400 – above | ₹8 | ₹80 |
Indian tariffs are telescopic — each slab is charged at its own rate, not the whole bill at the top rate. At 300 units a month the effective rate here works out to about ₹3.73 per unit, which is the figure that matters for solar, because that is what each generated unit saves you.
Solar cuts from the top slab down.
Your first generated units displace your most expensive units, so the effective saving
per unit is higher than your average tariff at the start, and falls as you offset more.
This is why partial offset is often better value per rupee than full offset.
Tamil Nadu uses net billing.
Surplus is bought back at ₹2.8 against a retail tariff of about
₹3.73. Sizing beyond your own consumption returns far less
here than it would under net metering — consider sizing closer to your daytime usage
and shifting heavy loads into daylight hours.
Tariff slabs and metering rules are revised by state regulators. These figures are
benchmarks last reviewed
August 2026 —
confirm current values with your DISCOM before committing to a system.