Electricity bill:
units, rate, fixed charge and duty explained

What sits on a typical bill

Open a bill from your distribution company and the same few building blocks keep appearing. Consumption is measured in kilowatt-hours, which most people call units: one unit is one kilowatt used for one hour. The meter records the reading at the start and end of the billing period, and the difference is what you are charged for.

• Energy charge: units consumed multiplied by the tariff rate.
• Fixed or demand charge: a flat amount, or one tied to your sanctioned load in kW.
• Fuel or power-purchase adjustment: a per-unit surcharge that can move month to month.
• Electricity duty and taxes: usually a percentage on the charges above.
• Arrears, rounding, meter rent and subsidies where they apply.

Where a bill shows a previous reading, a present reading and a line for units billed, subtract the two readings yourself as the first check. A mismatch between that difference and the units billed is the quickest way to spot a data-entry slip, a multiplier or an estimate.

The bill formula

If a utility prints its rate as paise per unit, divide by 100 first. A rate of 700 paise per kWh is ₹7.

Not every utility prints every line. Some fold the fuel adjustment into the per-unit rate, some add a separate line for meter rent, and some show a rebate for paying online or on time. The structure is the same, so identify each printed line as energy, fixed, adjustment or tax and the total will reconcile.

Worked example with a single rate

The 5% figure is only there to show the mechanics; your state sets its own duty, and some bills tax only the energy portion.

Why slab tariffs change the answer

Many utilities charge a lower rate for the first block of units and a higher rate as consumption climbs. The rate for each block applies only to the units inside that block, not to the whole reading. People often mistake this and multiply all their units by the top rate.

Adding the same ₹180 fixed charge makes ₹2,280 before duty, which is ₹350 less than the single-rate figure of ₹2,630. The slab shape is why a bill can jump sharply once you cross a threshold.

Some tariffs work the other way and apply one rate to all units once a threshold is crossed, which is called a telescopic versus a non-telescopic structure. Ask your utility or read the tariff order to learn which applies, because the same 350 units can cost quite different amounts under the two.

Why a longer billing cycle looks like higher use

A bill covers the days between two meter readings, and that period is not always a calendar month. A reading taken after 33 days will include about 14% more days than one taken after 29, so the units and the rupees rise even if you changed nothing.

Dividing the total by the number of days gives a figure you can compare month to month. On ₹2,630 for a 30-day cycle the daily cost is about ₹87.67; the same ₹2,630 over 33 days is ₹79.70 per day, and over 29 days ₹90.69. If your tariff gives a different slab allowance per month, a short cycle can also push you into a higher slab sooner, so check how the slab limits are prorated on your bill.

Rebuilding your own bill

1. 1Subtract the previous meter reading from the current one, applying any meter multiplier printed on the bill.
2. 2Find the tariff category on the bill, such as domestic or commercial, and the rates for it.
3. 3Apply each slab to its own block of units.
4. 4Add the fixed charge, then the fuel adjustment per unit.
5. 5Apply duty to the portion your state taxes and add arrears or subtract subsidy.

If your rebuilt figure is close but not exact, the gap is usually a fuel adjustment, a prorated billing period or a rounding rule. A calculator with an optional slab input makes this check quick.

Meter multipliers and estimated readings

Some connections, usually larger ones, use a meter that sits behind a current transformer. The reading on the display is then multiplied by a constant printed on the bill, often called the multiplying factor. A difference of 40 units shown on the dial with a factor of 10 means 400 billed units, which is a common source of confusion when people compare a bill with their own estimate.

When the meter could not be read, the utility may bill an estimated amount based on past usage. The next actual reading corrects it, so a low estimate is followed by a bigger bill. If an estimate looks wrong, send the utility a photo of the meter with the date, and ask for the bill to be revised.

Keeping the number useful

Billing months differ in length, so compare cost per day rather than the headline total when you are judging a change in habits. A 33-day cycle against a 29-day cycle can raise usage by 14% with no change in behaviour at all.

A bill that spikes after a few cool or hot weeks usually reflects heating or cooling loads. Those run for hours and draw a lot, so the extra kilowatt-hours land in your highest slab. Looking at the daily average units across several months tells you whether a spike is seasonal or a sign of a faulty appliance.