What does 1 unit of electricity mean?
1 unit means 1 kilowatt-hour, written as 1 kWh. A 1,000 W appliance running for one hour uses 1 kWh. A 100 W appliance running for ten hours also uses 1 kWh.
Electricity & Appliances calculator
Electricity Bill Calculator
Estimate appliance running cost, monthly electricity use, a flat-rate bill, and savings from lower daily usage with editable ₹/unit or global currency inputs.
Interactive calculator
Estimate electricity use, bill, or savings
Check one appliance, estimate a monthly bill from units, or compare a lower daily runtime. One unit of electricity means 1 kWh.
What to do next
Continue your decision
Formula, example, assumptions, and FAQs — open any section for the detail.
Formula
Electricity units and appliance use
1 unit = 1 kWh · kWh = watts × hours × days × quantity ÷ 1000A 1,200 W appliance used for 2 hours on 30 days uses 72 kWh, or 72 units, in that monthly estimate. When wattage is entered in kW, it is used directly instead of dividing by 1,000.
Appliance running cost
Cost = kWh × unit rate · Cost per hour = wattage in kW × unit rate × quantityAt ₹7.50 per unit, 72 kWh costs about ₹540. Use the rate from your own bill because country, state, provider, plan, and slab rules vary.
Monthly bill estimate
Estimated bill = monthly units × unit rate + fixed / other charges + taxes / extra chargesThis is a transparent flat-rate estimate. It does not calculate provider-specific slabs, subsidies, time-of-use pricing, minimum charges, fuel adjustments, or local taxes automatically.
Savings from lower usage
Monthly savings = current monthly cost − lower-hours monthly cost · Yearly savings = monthly savings × 12The savings mode holds wattage, days, quantity, and unit rate constant so you can isolate the effect of reducing daily runtime.
Usage pressure signal
Appliance: below 30 kWh low, 30 to under 100 medium, 100+ high · Monthly bill mode: below 100 low, 100 to under 300 medium, 300+ highThese are simple attention bands for this calculator, not official tariff slabs or a judgement about what a household should consume. Climate, family size, appliance mix, and local conditions matter.
Worked example
Appliance cost, monthly bill, and one-hour saving examples
An appliance is rated at 1,200 W and runs 2 hours a day for 30 days at ₹7.50 per unit. A separate monthly bill check uses 250 units, ₹200 fixed charges, and ₹75 extra charges.
Calculation:Appliance use: 1,200 × 2 × 30 ÷ 1,000 = 72 kWh; cost: 72 × ₹7.50 = ₹540/month. Monthly bill: 250 × ₹7.50 + ₹200 + ₹75 = ₹2,150. Reducing the 1,200 W appliance by 1 hour a day saves 1.2 × 1 × 30 × ₹7.50 = ₹270/month.
Result:The appliance alone may add about ₹540 a month under the entered assumptions. The full flat-rate bill estimate is ₹2,150, while a one-hour daily reduction for that appliance is worth about ₹270 a month. Real bills can differ because of slabs, fixed charges, taxes, subsidies, and actual appliance cycling.
Assumptions
- One electricity unit is treated as one kilowatt-hour (kWh).
- Appliance wattage is an estimate of power draw; preset values are editable and are not exact for every model.
- Daily runtime is the time the appliance actively draws the entered wattage, not merely the time it remains plugged in.
- Monthly appliance use follows the entered days per month, and the yearly estimate is that monthly pattern multiplied by twelve.
- Monthly bill mode uses one flat unit rate entered by the user and adds only the fixed and extra amounts entered.
- Average daily bill figures use a 30-day planning month.
- Currency is a display choice only; no exchange-rate conversion is performed.
- AC star rating, inverter operation, appliance age, settings, weather, room conditions, voltage, and maintenance can change real consumption.
- AC, geyser, and water pump usage can change bills quickly because their wattage or runtime is often high.
- State tariffs and slab rates can change the final bill, so the entered flat rate is only a planning input.
- Refrigerators, AC compressors, pumps, heaters, and other cycling loads may not draw nameplate wattage continuously.
Common mistakes
- Confusing watts or kilowatts, which measure power, with kWh or units, which measure energy used over time.
- Entering 1.5 as watts when the appliance is rated 1.5 kW, or entering 1,500 as kW.
- Using the cheapest slab rate for every unit when the actual bill uses multiple slabs or additional per-unit charges.
- Assuming a refrigerator uses its full rated wattage for all 24 hours even though the compressor cycles.
- Treating an AC tonnage preset as exact without checking star rating, inverter type, rated input, temperature setting, or actual compressor runtime.
- Leaving out the quantity when several fans, bulbs, computers, or other identical appliances run together.
- Adding fixed charges or taxes again when they are already included in the effective unit rate used.
- Treating the estimate as an electricity-board bill guarantee.
Accuracy notes
The arithmetic is deterministic and supports W or kW input. kWh is rounded to three decimal places and money to two decimal places for display. Accuracy depends mainly on real wattage, active runtime, quantity, unit rate, and whether cycling or variable-power appliances are represented realistically. The pressure labels are attention bands, not official consumption standards.
Frequently asked questions
Where can I find the electricity rate per unit?
Check your electricity bill for energy charge, unit rate, tariff, or price per kWh. If the bill uses slabs, divide the relevant energy charges by units only when that produces a useful effective rate, and keep fixed charges separate.
Are the appliance preset wattages exact?
No. They are starting estimates only. Check the appliance label, manual, annual energy label, or a suitable energy monitor. Actual draw can change with model, age, speed, temperature, load, and operating cycle.
Why can an AC use less or more than the preset?
AC input varies with tonnage, star rating, inverter operation, room heat, outdoor temperature, thermostat setting, maintenance, and compressor cycling. Use rated input or measured consumption from your specific model when possible.
Should I enter 24 hours for a refrigerator?
Only with care. A refrigerator is plugged in all day but its compressor cycles. Multiplying nameplate watts by 24 can overstate use. An annual kWh label or measured average is usually better.
Does monthly bill mode calculate Indian state tariff slabs?
No. Enter your own flat or effective unit rate and known extra amounts. State tariffs, slabs, subsidies, fixed charges, taxes, and provider rules can change the final bill and are not hardcoded here.
Can I use this calculator outside India?
Yes. Replace ₹ with your currency symbol or short code and enter your own cost per kWh. The formulas are global, but the calculator does not convert currency or infer local tariffs.
Why is cost zero when kWh is not zero?
The unit rate was entered as zero. This is allowed when you only want a usage estimate. Enter the rate from your bill to calculate money.
This calculator provides a flat-rate planning estimate, not an official electricity-board, utility, or provider bill. Actual charges may use slabs, fixed or demand charges, taxes, subsidies, fuel adjustments, time-of-use rates, minimum charges, meter rules, or other local terms. Verify important estimates against your appliance data and electricity bill.Read the full disclaimer.