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Electricity is billed by the kilowatt-hour (kWh) — one "unit" is 1000 watts running for one hour. Multiply an appliance's power by how long it runs to get the energy, then multiply by your tariff to get the cost. The tariff symbol here is ₹, but the maths works for any currency.
| Quantity | Formula |
|---|---|
| Energy per day | kWh = P(W) × hours × quantity / 1000 |
| Daily cost | kWh/day × tariff |
| Monthly cost | daily cost × 30 |
| Yearly cost | daily cost × 365 |
A handy rule: a 1000 W (1 kW) device running for 1 hour uses exactly 1 kWh — one unit of electricity.
A kilowatt-hour is the energy of 1000 watts running for one hour. It is the "unit" your electricity meter counts and your bill charges for.
Multiply its power in kilowatts by the hours used to get kWh, then multiply by your tariff. For example 1.5 kW × 2 h × ₹8 = ₹24.
Divide watts by 1000 to get kilowatts, then multiply by hours of use. So 100 W for 8 h is 0.1 kW × 8 = 0.8 kWh.
Many do, but motors, fridges, and air-conditioners cycle on and off, so their average power is lower than the nameplate. Use the average running power for a realistic estimate.
Use the per-unit (per-kWh) rate from your electricity bill. Some tariffs are tiered or time-of-use, in which case use the rate for the relevant slab or time.
Bills often add fixed charges, taxes, and tiered rates on top of the energy cost. This calculator gives the pure energy cost of the appliances you enter.
Small but constant — a device drawing 5 W on standby all year uses about 44 kWh. Multiply by your tariff to see it adds up across many gadgets.
Use efficient appliances (LED lighting, inverter ACs), run high-power devices less, switch off standby loads, and shift usage to cheaper time-of-use periods where available.
Check the label or nameplate (often in watts, or volts × amps). A plug-in energy meter gives the most accurate real-world figure including cycling.
Yes — on an electricity bill "1 unit" means 1 kWh.
Multiply the kWh added to the battery by your tariff. Charging losses add roughly 10–15%, so add a little for a real-world figure.
Only if it runs as long. Cost depends on power × time, so a high-wattage device used briefly can cost less than a low-wattage one left on all day.
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