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How to Read Your TNEB / TANGEDCO Electricity Bill

5 min read · Updated 21 July 2026

Tamil Nadu bills are the most misread in India for one simple reason: TANGEDCO bills once every two months, so every slab, every free-unit limit and every comparison with other states must be done on a 2-month cycle. Add the free units (200 per cycle for most households since FY 2026-27) and the concession cliff at 500 units, and two similar households can see very different totals.

1. Bimonthly billing — the #1 source of confusion

Your "monthly" consumption is actually two months of units. When comparing with friends in other states — or using any calculator built on monthly slabs — halve your TNEB units first. Our Tamil Nadu calculator shows a monthly estimate; multiply by two to sanity-check a bimonthly bill.

2. The free units — 200 or 100, depending on your total

Every domestic consumer gets free units each 2-month cycle. Since FY 2026-27 (G.O. (Ms) No. 50, given effect by TNERC Order No. 5 of 2026), it is 200 units free if the cycle total stays within 500 units, and 100 free units above that — earlier it was a flat 100 for everyone. So crossing 500 units does two things at once: your free allowance halves and the concessional treatment falls away. That's the "cliff" that makes a 510-unit cycle cost far more than a 490-unit one.

3. The slab ladder

Above the free block, slabs step at 200, 500 and 1000 units per cycle (slab-wise), with the top slab applying beyond 1000. Current per-unit rates are on the TANGEDCO tariff page. The fixed charge for domestic connections is a modest flat amount per cycle, and electricity duty adds 5% on the energy charges.

4. Verify the total

  1. Confirm the reading dates span ~60 days — a longer cycle silently pushes units into higher slabs.
  2. Check units = (current − previous) × MF.
  3. Recompute: free units (200 within a ≤500-unit cycle, else 100) → slab ladder on the rest → duty. Or enter half your cycle units in the calculator and double the result.
  4. A jump with unchanged habits usually means the cycle crossed 500 units — see our bill-increase guide.

Frequently asked questions

Why is my TNEB bill for two months?
TANGEDCO bills domestic consumers bimonthly — meters are read every ~60 days and all slabs and free-unit limits are defined per 2-month cycle. Halve the units before comparing with monthly-billing states.
How many free electricity units does Tamil Nadu give per cycle?
Since FY 2026-27, 200 units free per 2-month cycle for domestic consumers whose cycle total stays within 500 units, and 100 free units above that (earlier it was a flat 100 for all). The allowance halving at 500 units is part of why the bill jumps at that threshold.
Why did my TNEB bill jump although my usage barely changed?
The most common cause is crossing the 500-unit threshold for the 2-month cycle, which removes the concessional rates for the entire bill — a 20-unit increase can add a disproportionate amount. Longer reading cycles and estimated readings are the next suspects.
Does TANGEDCO charge electricity duty?
Yes — Tamil Nadu adds electricity duty at 5% on the energy charges, one of the lower rates among large states. It appears as a separate line after the slab charges.

Now check your own bill

Reading is half the job — run your own units through your DISCOM's real slab rates, fixed charges and FPPA and get an itemised bill in seconds. Free, no sign-up.

Open the electricity bill calculator →

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General guidance based on publicly available tariff orders and regulations; specifics vary by state, DISCOM and consumer category. Verify against your DISCOM's official schedule or your printed bill.