How is the TNEB electricity bill calculated?

TANGEDCO bills domestic consumers bi-monthly using telescopic slabs, which means each slab rate applies only to the units falling inside that slab — not to your whole consumption. Your energy charge is the sum of each slab, and a fixed charge based on your consumption band is added on top. The first 100 units in every bi-monthly cycle are free for domestic consumers.

Are the first 100 units free in Tamil Nadu?

Yes. Domestic (LT Tariff IA) consumers receive the first 100 units of every bi-monthly billing cycle free of energy charges. This applies regardless of total consumption — even a household using 900 units pays nothing for the first 100. The free units cover energy charges only; fixed charges still apply.

What are the current TNEB domestic tariff slabs?

For bi-monthly consumption up to 500 units: 0–100 free, 101–200 at ₹2.35/unit, 201–400 at ₹4.70/unit, 401–500 at ₹6.30/unit. Above 500 units the slab structure changes: 0–100 free, 101–400 at ₹4.70, 401–500 at ₹6.30, 501–600 at ₹8.40, 601–800 at ₹9.45, 801–1000 at ₹10.50, and above 1000 at ₹11.55 per unit.

Why does my bill jump sharply after 500 units?

Because crossing 500 units moves you to a different slab table, not just a higher marginal rate. Under 500 units, the 101–200 band is charged at ₹2.35. Over 500 units, that same band is recomputed at ₹4.70. So a household that goes from 499 to 501 units sees a disproportionate rise — the cheap band is retroactively repriced for the whole bill.

How do I calculate my TNEB bill from meter readings?

Subtract your previous meter reading from the current reading to get units consumed in the cycle. Enter that figure above and the calculator applies the correct slab table, adds the fixed charge, and shows a full band-by-band breakdown. Both readings appear on your existing bill, so you can verify last cycle against the calculator to confirm you are on the expected tariff.

Is TNEB billing monthly or bi-monthly?

Domestic connections in Tamil Nadu are billed bi-monthly, so meters are read once every two months. This matters when comparing rates with other states: a 400-unit TNEB bill covers two months, equivalent to 200 units a month. The calculator has a monthly mode that doubles your figure before applying the bi-monthly slabs.

What is the fixed charge on a TNEB bill?

A fixed charge is levied per service connection per billing cycle, based on your consumption band rather than your load. It is separate from energy charges and is payable even during the free-unit portion of your consumption. The calculator shows it as a distinct line so you can reconcile it against your printed bill.

How can I reduce my Tamil Nadu electricity bill?

Because the tariff is telescopic and steps up sharply, the marginal unit matters far more than the average. Staying below 500 units bi-monthly keeps your entire bill on the cheaper slab table, which is often worth more than any single efficiency measure. Air conditioning, geysers and old refrigerators dominate consumption in most Tamil Nadu households — a 5-star inverter AC typically cuts cooling consumption by 30–40% against an older unit.

Tamil Nadu Electricity Bill Calculator — TNEB / TANGEDCO Bill Online

Units consumed

Billing period

Enter your units consumed or meter readings to calculate your TNEB bill.

How TNEB Domestic Billing Works

Telescopic slabs, not a flat rate

TANGEDCO uses a telescopic tariff. That means each rate applies only to the units inside its own band, not to your entire consumption. A 450-unit bill is not 450 × the top rate — it is 100 units free, then 100 at ₹2.35, then 200 at ₹4.70, then 50 at ₹6.30. This is why your effective per-unit cost is always lower than the headline slab rate you have reached.

Two tariff tables, and the 500-unit cliff

The structural quirk in TNEB billing is that there are two different slab tables, selected by your total consumption:

Up to 500 units (bi-monthly)

Units	Rate
0–100	Free
101–200	₹2.35
201–400	₹4.70
401–500	₹6.30

Above 500 units (bi-monthly)

Units	Rate
0–100	Free
101–400	₹4.70
401–500	₹6.30
501–600	₹8.40
601–800	₹9.45
801–1000	₹10.50
Above 1000	₹11.55

Notice what happens at the boundary. Below 500 units the 101–200 band costs ₹2.35. Above 500 units that same band is repriced at ₹4.70. A household going from 499 to 501 units does not just pay for two extra units — the cheap band is recalculated across the whole bill. This is the single biggest reason TNEB bills jump unexpectedly.

Worked example: 450 units

Slab	Units	Rate	Charge
1–100	100	Free	₹0.00
101–200	100	₹2.35	₹235.00
201–400	200	₹4.70	₹940.00
401–450	50	₹6.30	₹315.00
Energy charges			₹1,490.00

Add the fixed charge for the band and you have the payable amount. The effective rate works out to roughly ₹3.40 per unit — well below the ₹6.30 top slab the household reached.

Reading your bill correctly

Units consumed = current reading − previous reading. Both appear on the printed bill.
Bi-monthly means the figure covers two months, so divide by two before comparing with a monthly bill from another state.
Fixed charges are per service connection per cycle and apply even if your consumption falls entirely inside the free band.
Assessment vs actual — if the meter could not be read, TANGEDCO raises a provisional assessment and adjusts it in the next cycle, which can make one bill look abnormally high or low.

Where the units actually go

Appliance	Typical load	Units per bi-monthly cycle
1.5 ton AC, 6 hrs/day	1,500 W	~540
Refrigerator (older, 300 L)	150 W avg	~220
Geyser, 1 hr/day	2,000 W	~120
Ceiling fan, 12 hrs/day × 3	75 W each	~160
LED lighting, whole house	100 W	~36
Washing machine, 4 loads/week	500 W	~20

Air conditioning alone can push a household from the cheap slab table into the expensive one, which is why a single AC often doubles a Tamil Nadu bill rather than adding a proportional amount.

Tariffs are set by the Tamil Nadu Electricity Regulatory Commission and revised periodically. The slabs used here reflect the domestic LT Tariff IA structure in general use; fixed charges in particular vary by consumption band and tariff order. Always reconcile against your printed TANGEDCO bill, and treat this calculator as an estimate.

Tamil Nadu Electricity Bill Calculator