Electricity Bill Calculator - kWh Cost, Tariffs and Monthly Use

Agarapu Ramesh — Editor and content reviewer
Editorially reviewed Reviewed by Agarapu Ramesh, science educator (chemistry). LinkedIn
Last reviewed: May 2026 | Standard electrical engineering formulas

An electric bill is mostly kWh x rate, then the utility adds fixed charges, taxes and sometimes slab pricing or demand charges. The calculator gives the clean number first so you can see what the appliance is really doing.

Formula at a glance

  • energy cost = kWh x rate per kWh
  • monthly kWh = watts x hours per day x days / 1000
  • total bill = energy charge + fixed charges + taxes

Field note: Do not average one appliance across the whole bill unless you know the hours. Guessing hours is where most home energy audits go sideways.

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Electricity Bill Calculator

Calculate your energy cost

W
hrs/day
days
USD/kWh
Result
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Formula

kWhkWh = W × hrs × days / 1000
CostCost = kWh x rate

Common Appliance Wattage

Appliance Watts
LED Bulb 10W
Laptop 50W
TV (LED 50") 100W
Refrigerator 150W
AC Window 1000W
Space Heater 1500W
Hair Dryer 1800W

Related

Energy ConsumptionkW to kWhEnergy Cost

How to use the Electricity Bill Calculator

Use this as a unit check for energy, power and time. Keep the time period honest, because a one-hour run and a one-month run can make the same load look completely different.

Worked example

Example: a 1,500 W appliance running 2 hours a day for 30 days uses 90 kWh. At $0.18 per kWh, the energy charge is $16.20 before fixed fees.

Practical checks before you trust the number

  • Check whether your tariff has slabs. The last unit can cost more than the first unit.
  • Air conditioning and water heating usually dominate the bill.
  • Demand charges can matter for commercial accounts even when kWh looks normal.

Common mistake

Do not average one appliance across the whole bill unless you know the hours. Guessing hours is where most home energy audits go sideways.

Sources and references

Related calculators

Frequently Asked Questions

Bill = kWh used × tariff per kWh + fixed charges + taxes. Example: 200 kWh × I6/kWh = I1200, plus a fixed charge of I100 and 18% GST → total ≈ I1534. Always check your tariff structure — most utilities have slab rates that increase with usage.

100 × your tariff per kWh, plus fixed and tax components. At I6/kWh, energy charge = I600. Plus fixed (I50–I200) and taxes (typically 5 to 18% GST). Total around I700 to I900 depending on slab and state.

Monthly cost = (W × hours per day × 30 ÷ 1000) × tariff. Example: a 1000 W AC running 6 hours/day at I6/kWh → (1000 × 6 × 30 ÷ 1000) × 6 = I1080/month. Run this per appliance to identify your top energy spenders.

Use the slab rate that applies to your usage band. For low usage (0 to 100 kWh), tariffs may be I3 to I5/kWh. Above 300 kWh, slab rates can jump to I8 to I10/kWh in many states. Check your latest electricity bill for the exact rate breakdown — they vary by state, season, and discom.

Add fixed charges directly to the energy charge total. Fixed charges depend on sanctioned load (kW) — usually I50 to I100 per kW per month. So a 5 kW connection might have I250 to I500 fixed charge regardless of consumption. Add GST and any duty cesses on top.

Because the bill includes more than just kWh × rate. Fixed charges, slab pricing (higher rates at higher usage), GST, electricity duty, fuel adjustment surcharge, and meter rent all add up. Crunch the bill line by line — you'll often find 20 to 30% beyond the basic kWh charge.

Yes. Enter AC kW, daily runtime, and tariff to estimate monthly cost. Example: 1.5 kW × 8 h × 30 days × I7/kWh = I2520/month. Helps customers decide between 3-star and 5-star units — the price difference often pays back in 2 to 3 summers.