How to read your electricity bill — and why it suddenly jumped

Most people read an electricity bill the way they read a restaurant receipt: a look at the number at the bottom, a wince, and payment. That works until the month the number doubles and nobody in the house can say why.

Each line on the bill is set by someone different — the state regulator, the state government, a formula that moves every month — and the energy charge is priced in slabs whose rate depends on how far up you have climbed. Once you can name the lines, a jump stops being a mystery and becomes a question you can check. This guide goes through the lines, works one real bill to the rupee from a current tariff order, and ends with how to dispute a bill that is actually wrong.

The lines on the bill, one at a time

Layouts differ from discom to discom, and so do the names. The components underneath are much the same everywhere.

The fixed charge is the line people overlook, because it does not move with use. Where a state charges it per kilowatt, a higher sanctioned load raises the bill even in a month the house stood empty. Not every state charges it on homes at all: Tamil Nadu's current tariff order sets the fixed charge for its domestic category, LT I-A, at nil.

The surcharge line is the one that moves without an announcement. Under rule 14 of the Electricity (Amendment) Rules, 2022, notified by the Ministry of Power on 29 December 2022, each state regulator has to set a formula under which changes in the cost of fuel or purchased power are “automatically passed through in the consumer tariff, on a monthly basis”, with a true-up once a year. A surcharge of up to 5% is recovered automatically; above that, the first 5% plus 90% of the rest, with the remainder left for the regulator to approve later. Delhi's regulator spells out the arithmetic: a 20% claim lets the discom bill 18.5% straight away. The central rules call it FPPAS; Delhi's regulations call it PPAC; other states use their own acronyms. Whatever the name, it should be a published per-unit rate you can look up.

Electricity duty is not the regulator's charge. It is the state government's, and its rate varies from state to state. Tamil Nadu's tariff order keeps the duty outside the tariff and requires the rate, and the government order it is levied under, to be printed on the bill itself. That is a good test for any line on any bill: if it has no stated basis, ask for one.

Slabs: why the last units cost the most

Domestic energy charges are telescopic. The first block of units is billed at the lowest rate, the next block at a higher one, and so on, with each rate applying only to the units inside its own slab. Using more makes your next unit dearer without repricing the units beneath it. That is the theory, and most of the time it holds.

Two things can break it. The first is a cliff: some states switch you to a different table altogether once your total crosses a line, so the cheap units at the bottom stop being cheap. The second is the billing period. A slab table is written for a period. Tamil Nadu's order states every domestic slab twice — per month, and “for two months” — with the two-month boundaries exactly double. A two-month bill measured against a monthly table would push most of a household's units into the top slabs, so check that the slabs on your bill match the number of months it covers.

Billing periods also stretch. If the meter is read ten days late, the bill covers ten more days of use against the same slab boundaries, which can tip a household over one unless the discom pro-rates the slabs for the extra days. Ask whether yours does. Before anything else on a bill that looks wrong, read the dates of the previous and present readings.

A real bill, worked through: Tamil Nadu, 2026

Tamil Nadu shows all of this at once: its slabs are steep, its domestic bills run on a two-month cycle, and the state government pays a large share of every one. The rates below come from the Tamil Nadu Electricity Regulatory Commission's Tariff Order No. 6 of 2025, dated 30 June 2025 and in force from 1 July 2025, and from its two subsidy orders for 2026-27: Order No. 4 of 2026, dated 27 April 2026, and Order No. 5 of 2026, dated 26 May 2026. When we checked the commission's list of tariff orders on 9 October 2026, no tariff revision for 2026-27 had been issued.

Every domestic slab carries two prices. The tariff is what the regulator says a unit costs; the subsidy is what the state government pays the discom per unit on your behalf; what you pay is the difference. Which subsidy you get depends on your total. From 10 May 2026, a household using up to 500 units in two months pays nothing for its first 200. Cross 500 and only the first 100 are free, and the rates for the units above them change too.

Take a Chennai flat with one air conditioner running through a hot April and May, whose two-month bill reads 520 units.

That comes to ₹2,208 in energy charges. Had the same flat used 500 units — twenty fewer, about ten a month — it would have been billed on the up-to-500 table instead: 200 units free, 200 at ₹4.70 and 100 at ₹6.30, for ₹1,570. Those twenty units cost ₹638, nearly ₹32 each, while the slab rate printed against them is ₹8.40. That is the cliff, and in Tamil Nadu it is the most common way a bill jumps without the household doing anything very different.

Two smaller lessons sit in the same table. The 101–200 slab costs the 520-unit household ₹4.70 a unit and the 500-unit household nothing: the same unit, priced by your total. And the May 2026 order made bills under the line cheaper, not dearer. Before 10 May, units 101–200 were billed at ₹2.35 even for households under 500, so the same 500 units cost ₹1,805.

These are energy charges only. Tamil Nadu sets no fixed charge for LT I-A, and electricity tax, where it applies, comes on top and has to be stated on the bill.

Why your bill jumped: the usual suspects

Work down this list in order. The first few explain most surprises, and you can check them from the bill alone.

1. You crossed a line. A slab boundary, or a cliff like Tamil Nadu's at 500 units. Summer cooling is the usual reason. Compare this bill's units with the same months last year, not with the previous bill.
2. The billing period was longer. Check the two reading dates. More days means more units against the same slabs.
3. The last bill was an estimate. If the previous bill was provisional and too low, this one carries the catch-up — a season of under-billing arriving at once, often in the higher slabs. The bill should show whether each reading was actual.
4. The surcharge moved. Where your state levies a monthly fuel and power purchase surcharge, a rise in what the discom pays for power reaches your bill within weeks, with no new tariff order.
5. The tariff or the subsidy changed. Regulators usually revise tariffs once a year; governments change subsidies when they choose. Both are public. The Rights of Consumers Rules require a discom to notify any change in tariff, including fuel surcharge, a full billing cycle ahead, on its website and on the bill.
6. Your sanctioned load went up. Where the fixed charge is per kW, a higher sanctioned load costs you every month. Under the 2023 amendment to the Rights of Consumers Rules, the load is to be revised upward only if you exceed it at least three times in a financial year, and a newly fitted smart meter's readings cannot be used to penalise demand from before it was installed.
7. The meter is wrong. It happens, but it is the last explanation to reach for, not the first. There is a formal way to test it, set out below.

Estimated bills, smart meters and prepaid

The Electricity (Rights of Consumers) Rules, 2020, notified by the central government on 31 December 2020, set a national floor that every state's rules build on. On reading and billing, the meter has to be read at least once in every billing cycle, in villages as well as towns. The bill has to be based on an actual reading and reach you at least ten days before the due date. The discom has to upload it to its website on the day it is generated, and keep your last year of bills there.

Estimates are capped. A discom may not generate more than two provisional bills for a consumer in a financial year, and if provisional billing runs on for more than two billing cycles, outside force majeure, you may refuse to pay until a bill is raised on an actual reading. If the meter could not be read on two consecutive reading dates — a locked gate, a meter inside the flat — you can send a photograph of it, showing the reading and the date, from your registered mobile number or e-mail, and the discom may then skip the provisional bill altogether.

Going away for a few months? Tell the discom in writing and pay the fixed charges for the period in advance. The rules then say it shall not send you a provisional bill, and shall not disconnect you.

Smart meters change the evidence more than the rules. Under the 2023 amendment they are read remotely at least once a day, and the data is to be shared with you, so a smart-meter bill should be easier to check: the consumption record ought to account for every unit. On a prepaid meter, the discom issues a bill when you ask for one. The same amendment brought in time-of-day tariffs for domestic consumers, to apply once a smart meter is installed and from 1 April 2025 at the latest. Whether your state prices different hours differently, and by how much, is in your tariff order.

Disputing a bill that is wrong

Most bill disputes end at the first step, because most errors are clerical: a misread digit, the wrong slab table, an estimate nobody reversed. Go in order.

1. Photograph the meter. Reading and date both visible, taken today. That one picture settles more disputes than any letter.
2. Do the arithmetic. Present reading minus previous, the days between them, the slabs for that period, the surcharge rate. If your figure differs from the bill's, you now know exactly where.
3. Complain in writing, and keep the reference number. The rules require every bill to name the authority that handles billing complaints, and the discom's website to say the same. Use the discom's portal, app or office rather than a phone call alone, so there is a date and a number on record. We list every discom, with its helplines, on our discoms page.
4. If the meter itself is the question, ask for a test. The discom has to test it within the time your regulator sets, which cannot exceed thirty days from your complaint, and give you a signed copy of the report; any excess billed is adjusted in later bills. Under the 2024 amendment, if you complain that readings do not match your use, it must also fit an additional meter within five days and run it for at least three months. If you dispute the discom's test, you can have the meter tested at a third-party lab approved by the regulator, and whichever side the result goes against pays for that test.
5. Escalate to the CGRF, then the Ombudsman. If the discom does not resolve it, take it to the Consumer Grievance Redressal Forum, which every discom must have. The rules say a grievance should normally be decided within thirty days and in no case beyond forty-five. After the forum, the next step is the Electricity Ombudsman appointed by your state regulator.

Do not let a disputed bill turn into a disconnection. Section 56 of the Electricity Act, 2003 says supply shall not be cut off while a dispute is pending if you deposit, under protest, either the amount claimed or your average monthly charge over the preceding six months for each month billed — whichever is less. Disconnection for non-payment also needs at least fifteen clear days' notice in writing. And a sum the discom failed to bill cannot be recovered more than two years after it first became due, unless it has been shown on your bills as arrears continuously since.

Getting a complaint registered, and getting it escalated when nothing moves, works the same way for a bill as for an outage. The step-by-step is in how to file a power cut complaint.

What else your discom owes you on paper

A correct bill is not the only promise. Most states pay compensation when the discom misses its own deadlines for restoring supply or fixing a fault: power cut compensation in India.

If a surge or a fault burned out an appliance, that is a separate claim with its own evidence — see claiming for appliance damage.

Planned outages are announced in advance, if you know where to look: how to find your area's shutdown schedule.

And if the bill has you pricing an inverter, size it from what you actually run, not from the shop's advice: the inverter and battery calculator.

Questions people actually ask