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ToolBoxGenie

Electricity Bill Calculator

Calculators · Added 18 August 2026

Work out where your electricity actually goes. List your appliances with their wattage and how long each runs, or start from a meter reading, then enter your own tariff — flat rate or rising slabs — to get an estimated monthly bill, a yearly figure, and a ranked breakdown of what is consuming the most.

Where do the units come from?
Appliances
ApplianceWattsQtyHours/dayDays/monthkWhRemove
9.7
54.0
36.0

Preset wattages are typical ratings, not a claim about your appliance. The plate on the back of yours is the real number, and a fridge or an air conditioner draws its rated power only while the compressor is running — enter the hours it is actually cooling, not the hours it is switched on.

Tariff structure
Slab rates
Firstunits atper unit
Thenunits atper unit
Thenunits atper unit

Leave the last slab's limit blank — it charges everything above the previous one. Slabs are telescopic: units are charged at the rate for the band they fall into, not at one rate for the whole bill.

Standing charge or meter rent.

%

Electricity duty, VAT or GST.

How to use the electricity bill calculator

  1. 1Choose whether to build up the units from appliances or enter a meter reading directly.
  2. 2Add each appliance with its wattage, how many you have, hours of use per day and days per month.
  3. 3Pick your tariff structure — one flat rate per unit, or slabs that rise with consumption.
  4. 4Enter the rates, the fixed monthly charge and any duty or tax percentage from your bill.
  5. 5Press Calculate for the estimated bill and the per-appliance breakdown.

Examples

A small flat

Input
6 LED bulbs, 3 fans, a fridge — 195 units at slab rates of 4.5, 6 and 8
Result
About ₹1,375 a month including a ₹100 fixed charge

Adding an air conditioner

Input
The same flat plus a 1.5-ton AC for 6 hours a day
Result
465 units — the bill roughly doubles, because the extra units land in the top slab

This is why slab tariffs punish a single high-draw appliance so heavily.

From a meter reading

Input
342 units this month, flat rate 6.5, fixed charge 100, 5% duty
Result
₹2,438 — an effective 7.13 per unit once the fixed charge and duty are included

About the electricity bill calculator

The arithmetic, in full

Energy in kilowatt-hours is power in kilowatts multiplied by time in hours. A 75-watt fan running 8 hours a day uses 75 ÷ 1000 × 8 = 0.6 units a day, or 18 units over a 30-day month. Three of them use 54. That is the whole calculation, repeated for each appliance and summed.

The money is then a separate step: units are charged against the tariff, a fixed monthly charge is added whether you used anything or not, and a duty or tax percentage is applied on top. The effective rate shown in the results is the total divided by the units — the number that tells you what an extra unit really costs you, including the share of the standing charge.

Where a domestic bill actually goes

In most homes, a small number of appliances dominate. Anything that heats or cools — air conditioning, water heaters, electric kettles, irons, ovens — draws between 1,000 and 3,000 watts, and a couple of hours a day of it outweighs everything else in the house combined.

Everything with a motor comes next: refrigerators, washing machines, pumps. Then, a long way behind, lighting and electronics. Replacing every bulb in a house with LEDs is worthwhile and saves real money, but it will not offset an air conditioner that runs six hours a night. The breakdown table exists to make that ordering visible rather than assumed.

Reading the breakdown on a slab tariff

The per-appliance cost column uses a blended effective rate, which spreads the cheap early units across everything. That is the fair way to attribute a shared bill, but it understates what cutting consumption is worth.

On a rising slab tariff, the units you remove come off the top slab first — the most expensive one. Turning off an appliance that accounts for 50 units a month on a tariff where the top band is 8.00 saves 400, not the 350 the blended rate suggests. Savings on a tiered tariff are always worth more than the average suggests, and the effect gets stronger the higher your consumption already is.

Frequently asked questions

What is a unit of electricity?
One unit is one kilowatt-hour: a 1,000-watt appliance running for one hour. A 9-watt LED bulb needs about 111 hours to use a single unit; a 1,500-watt air conditioner uses one every 40 minutes. That ratio, roughly 170 to one, is why lighting is almost never the thing worth optimising on a bill.
Why do I have to enter the tariff myself?
Because there is no such thing as a national electricity rate. Rates are set per utility, often per state, and they differ by connection type, by season and by the amount consumed. A built-in table would be confidently wrong for most visitors and would go stale within a year. The rates are printed on your bill, usually on the reverse — enter those and the estimate will actually match.
How do slab or tiered rates work?
They are telescopic: each band of units is charged at its own rate, not the whole bill at the rate for the band you land in. If the first 100 units cost 4.50 and the next 200 cost 6.00, a 250-unit month is charged 100 × 4.50 plus 150 × 6.00, not 250 × 6.00. Applying the top rate to everything is the most common error in home-made spreadsheets, and it overstates a large bill substantially.
Why does my actual bill differ from this estimate?
Real invoices include things that vary by utility and by month: fuel surcharges, meter rent, subsidies, arrears from a previous cycle, time-of-day rates, and rounding to whole units. Billing cycles are also rarely exactly 30 days. Compare the estimate against your last bill and adjust the tariff inputs until they agree — after that, the tool is a reliable way to test 'what if'.
Does a fridge really use its rated wattage all day?
No, and this is the biggest source of error in appliance-based estimates. A refrigerator's compressor cycles on and off, typically running 30–50% of the time depending on ambient temperature and how often the door opens. Air conditioners with inverter compressors do the same. Enter the hours the appliance is actually drawing power, not the hours it is switched on — for a fridge, 8 to 10 hours a day is a reasonable starting point.
What about standby power?
Devices left on standby draw a small but continuous load — typically 0.5 to 3 watts each, running 24 hours a day. Individually negligible, collectively often 20 to 50 units a year in a home with a lot of electronics. To include it, add a row with the total standby wattage and 24 hours a day.

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