How the TANGEDCO tariff and subsidy system actually works

Based on TNERC – T.O. No. 6 of 2025, dated 30-06-2025, effective 01-07-2025.

1. Domestic bills are "telescopic," not flat-rate

A telescopic tariff means your electricity bill is built up slab by slab, like a staircase. The first block of units you consume is billed at one rate, the next block at a (usually higher) rate, and so on — every consumer pays the same rate for the same slab of units, no matter how much they use overall.

What changes with total consumption in Tamil Nadu isn't the tariff rate itself, but the Government of Tamil Nadu subsidy applied to each slab. A household that stays under 100 units a month gets a larger subsidy on its 51–100 unit slab than a household that goes on to consume 400 units — even though both households pay the same gross tariff rate for that slab.

2. The four consumption bands

Which "band" decides your subsidy schedule depends on your total units for the billing period:

• Band A — up to 50 units/month: fully subsidised, effectively nil energy charge.
• Band B — 51 to 100 units/month: the 51–100 slab is subsidised at a reduced rate.
• Band C — 101 to 250 units/month: subsidy on the 51–100 slab tapers further, and two more slabs (101–200, 201–250) are added.
• Band D — 251 units and above/month: the smallest subsidy on early slabs, plus four additional higher-priced slabs up to 500+ units.

For bi-monthly billing, every threshold above is simply doubled (0–50 becomes 0–100, and so on), since Tamil Nadu bills most domestic consumers once every two months.

3. Worked example

Suppose a household consumes 320 units in a bi-monthly cycle. Because that total falls between 202 and 500 units (the bi-monthly equivalent of Band C's 101–250 units/month), the whole bill is worked out using Band C's subsidy schedule. Within Band C, the bill is then built up slab by slab: the first 100 units (bi-monthly) at a heavily subsidised rate, the next 100 at a lighter subsidy, and the remaining 120 units at the Band C rate for the 201–250 units/month slab (402–500 units bi-monthly). The calculator above works out exactly this, slab by slab, for any number of units you enter.

4. Other LT and HT categories

Non-domestic connections — shops, industries, educational institutions, places of worship, construction sites, EV charging stations and agricultural pump-sets — are billed differently. Most combine a per-unit energy charge with a separate fixed or demand charge based on your connected load (kW for low-tension/LT connections) or contract demand (kVA for high-tension/HT connections). Some categories, like power looms and cottage industries, also step up their energy rate once consumption crosses a threshold within the billing period. EV charging stations are billed differently again, with three separate rates depending on the time of day electricity is drawn.

5. What this calculator doesn't include

This tool estimates energy charges, Government subsidy and fixed/demand charges as published in the tariff order. It does not account for electricity duty, meter rent, taxes, arrears, penal charges for exceeding sanctioned load, power factor surcharges/incentives, or any other line-item that may appear on your official TANGEDCO bill. Treat the result as a planning estimate, not a substitute for your actual bill.