Electricity Bill Calculator

Electricity bills confuse because they stack three things: how many units (kWh) you used, a tariff that often rises in slabs the more you consume, and fixed charges or taxes on top. This calculator untangles them: enter your total units and your slab rates to price a bill accurately, or estimate any appliance’s monthly cost from its wattage and daily hours so you can see exactly which device is eating your money. The appliance estimator teaches the household’s real hierarchy of hunger. Anything that makes heat or cold — kettles, heaters, geysers, air conditioners, ovens — dwarfs everything electronic; a gaming PC at full tilt uses less than a modest room heater, and an LED bulb is nearly free to run. That hierarchy tells you where savings live: one degree of AC setpoint and shorter geyser runs outperform a month of unplugging phone chargers, whatever the group chats claim.

Quick Answer: Enter units used and up to three slab rates to price your bill, or use the appliance estimator: wattage × hours per day × days gives units and cost at your average rate.

Free Online Tool

Units used (kWh)

Slab 1 rate (per unit, first 100)
Slab 2 rate (next 200)
Slab 3 rate (above 300)

Fixed charge
Tax / duties (%)

—Estimated bill

—Average per unit

Appliance estimator

Wattage (W)
Hours per day
Days per month

How to Use the Electricity Bill Calculator

Read your units (kWh) from your meter or last bill.
Enter your tariff: a single rate, or slab rates with their unit limits.
Add any fixed charge and tax percentage from your bill.
Read the estimated total with the slab-by-slab breakdown.
Use the appliance estimator below to find your hungriest devices.

Key Features

Slab (tiered) tariff support with per-slab breakdown
Fixed charge and tax fields modelled on real bills
Appliance cost estimator from wattage and daily hours
Instant recalculation as you type
Free with no sign-up

Best Practices and Tips

One unit = 1 kWh: a 100 W bulb running 10 hours uses exactly 1 unit.
Air conditioners dominate most bills — a 1.5-ton AC can use 1.2–1.8 units per hour.
Slab tariffs punish the top units hardest; cutting usage just below a slab boundary saves disproportionately.
Compare your per-unit average (total ÷ units) between bills to spot tariff changes and meter issues.
Phantom loads (chargers, standby TVs) quietly add 5–10% to many homes’ usage.
Photograph your meter on the 1st of two consecutive months: real units between readings beat every estimate, and the difference teaches you your household’s true baseline within one cycle.

Common Mistakes to Avoid

Pricing every unit at the top slab rate — lower units are billed at lower slab prices.
Confusing watts with watt-hours: cost comes from watts × time.
Forgetting fixed charges and taxes, then wondering why the estimate is below the real bill.
Estimating an AC by its labelled peak watts rather than its cycling average.

Frequently Asked Questions

What is a unit of electricity?

One unit is one kilowatt-hour (kWh): the energy of a 1,000 W appliance running for one hour, or a 100 W appliance for ten hours.

How do slab tariffs work?

Usage is priced in blocks: for example the first 100 units at one rate, the next 100 at a higher rate, and everything above at the highest rate. Each block is charged at its own price.

How can I estimate an appliance’s monthly units?

Watts × hours used per day × days in the month, divided by 1,000. A 75 W fan for 10 hours a day over 30 days uses 22.5 units.

Why is my estimate lower than my real bill?

Real bills may add fuel adjustments, duties, arrears or minimum charges beyond the fixed charge and tax fields here.

Is this calculator free?

Yes — free, unlimited and no sign-up required.

Why is my real bill higher than the estimate?

Fixed charges, fuel adjustments, taxes and slab timing all sit outside the energy calculation. The estimate covers consumption — compare its units line with your bill’s units line to isolate the difference.