Why is there a security deposit on my Tamil Nadu electricity bill?

TNPDCL keeps a security deposit against about three months of your electricity charges. Every two years it compares the deposit it holds with your recent bills. If your bills went up, it asks you to pay an additional security deposit.

Reviewed every two years
Top-up: additional security deposit
Prepaid meters: no deposit

Check your deposit

How TNPDCL reviews the deposit

TNPDCL reviews the deposit of LT consumers once every two years.
For bi-monthly billing, the required deposit is 3 times your monthly average electricity charges for the last 12 months.
For monthly billing, the required deposit is 2 times your monthly average charges for the 12 months before April.
The average does not include incidental charges.
The deposit held includes the interest that TNPDCL credited to it.
Additional security deposit = required deposit minus the deposit held.
TNPDCL sends a separate notice, or makes a separate entry in the meter card. You get 30 days to pay.
TNPDCL can also send the demand by SMS or e-mail.
On your request, you can pay in 3 instalments that match your billing cycle.
A consumer who is not the owner and has no owner's consent letter must hold more.
That consumer holds 6 times the monthly average (bi-monthly billing) or 4 times (monthly billing).

If you hold more than needed

TNPDCL adjusts the excess against your next two bill demands.
It refunds any balance by cheque or direct bank credit before the due date of the third demand.
If you ask, TNPDCL must adjust the excess against more than two demands.

Deposit for a new connection

You pay an initial security deposit before supply starts, at the rate that TNERC fixes.
From 1 July 2025, a domestic single-phase connection pays Rs 330 per connection.
From 1 July 2025, a domestic three-phase connection pays Rs 995 per kW.
TNERC raises these rates each year by the change in the consumer price index or 6%, whichever is lower.
If you are not the owner and you give an indemnity bond, you pay twice the normal rate.

Interest and prepaid meters

TNPDCL pays interest at the bank rate or a higher rate that TNERC sets.
It credits the interest to your deposit account at the start of each financial year (April).
TNERC set the rate at 5.76% a year for 2026-27.
Interest counts full calendar months only and rounds to the nearest rupee.
You pay no security deposit if you take supply through a prepaid meter.

What we could not confirm

The current regulation does not say what happens if you do not pay. The Electricity Act lets a discom stop supply while the failure continues. Check with TNPDCL.
The latest deposit rates we found apply from 1 July 2025. We found no newer TNERC order for July 2026.
We found no official TNPDCL sample that shows how the bill or meter card labels the additional security deposit.
The latest consolidated Supply Code is a scanned copy. We built the review rules from the 2010 text and the later amendment gazettes.
Sources differ on when TNPDCL must tell you about the interest credit: before the end of June, or before the end of the year.

Questions

How often does TNPDCL ask for an additional security deposit?

For homes, TNPDCL reviews the deposit once every two years. It asks for more only if your last 12 months of charges show a shortfall.

Can I pay the additional security deposit in parts?

Yes. Ask TNPDCL, and you can pay it in 3 instalments that match your billing cycle.

What interest do I get on my deposit in 2026-27?

TNERC set 5.76% a year for 2026-27. TNPDCL credits the interest to your deposit each April.

What if my deposit is more than I need?

TNPDCL adjusts the excess against your next two demands. It refunds the balance before the due date of the third demand.

More tools

Tamil Nadu bill calculator Where to complain in Tamil Nadu Other states

Sources

Read on 16 October 2026.

ebbillcalc is not part of any discom or regulator. The regulations and your discom have the final word.