Mobile & Electronics

Electricity Cost Calculator

What a device costs to run per day, month and year, at your own tariff rather than a national average.

6 inputs Free, no sign-up

Your figures

From the rating plate, the adapter, or the back of the unit.

Use fewer for something you only run at weekends.

Rupees per unit (kWh), from your own bill. Tariffs differ by state, by connection and by how much you use, so this is the figure the result is most sensitive to.

Try an example

Result

Your result

Enter your figures and the result appears here.

Estimates only. Rates, fees and specifications change. Confirm against the official source before you rely on a figure — see our disclaimer.

About this calculator

A device's running cost is its wattage, its hours and your tariff. Nothing else, and none of the three can be guessed on your behalf — which is why this page asks for all of them rather than offering a menu of appliances.

The answer is the energy cost of that device. It is not your bill: a bill also carries a fixed charge, slab rates that climb with consumption, a fuel adjustment and duty. Use this to compare devices and habits, which is what it is good for.

How to use this calculator

  1. Find the wattage on the rating plate, the adapter, or the back of the unit.
  2. Enter how many hours a day it actually runs — not how long it is switched on at the wall, if the two differ.
  3. Adjust the days per month for something you only use at weekends.
  4. Enter your own rate per unit from your bill. It is the figure the answer is most sensitive to.

The formula

Units a day   = Watts x Hours / 1000
Cost a day    = Units a day x Rate
Cost a month  = Cost a day x Days a month
Cost a year   = Cost a month x 12

The rate is per kilowatt-hour, which is what a bill calls a unit. Where a tariff has slabs, the rate that matters for this calculation is the one your marginal consumption falls in — the slab you are in at the top of your usage, not the lowest one.

SymbolMeaningUnit
P Device power W
Hours Running hours a day h
Rate Tariff per unit Rs/kWh

Worked example

A 65 W laptop, 8 hours a day, 30 days a month, at ₹8.50 a unit:

Units a day  = 65 x 8 / 1000 = 0.52
Cost a day   = 0.52 x 8.50    = Rs 4.42
Cost a month = 4.42 x 30      = Rs 132.60
Cost a year                   = Rs 1,591.20

Notes and limits

  • This is the device's energy cost, not your bill. Fixed charges, slab pricing, fuel adjustment and duty are all additional and none of them is per-device.
  • A rating plate usually gives the maximum. A laptop rated 65 W draws that under load and far less while idle, so the real figure is lower than the rating suggests.
  • Air conditioners, fridges and anything thermostatic cycle on and off. Their average consumption is well below their rated power, and the hours figure should reflect running time rather than switched-on time.
  • Take the rate from your own bill. State tariffs differ widely and change.
  • For several devices at once, use the multi-device calculator.

What this calculation assumes

  • The device draws the wattage entered for the whole of the running time.
  • The rate applies to all consumption; slab pricing is not modelled.
  • The figure is the energy cost of this device only, not a bill.

Frequently asked questions

How do I calculate electricity cost per unit?

Multiply the device wattage by the hours it runs and divide by 1,000 to get units, then multiply by your rate per unit. A 65 W device for 8 hours is 0.52 units, which at Rs 8.50 is about Rs 4.42.

Why is my actual bill higher than this?

Because a bill is more than energy. It typically includes a fixed monthly charge, slab rates that rise with total consumption, a fuel or power purchase adjustment, and electricity duty - plus every other device in the house.

What wattage should I use for an air conditioner or fridge?

The rated power, with hours that reflect how long the compressor actually runs rather than how long the unit is switched on. Thermostatic appliances cycle, so switched-on time badly overstates consumption.

Where do I find my electricity rate?

On your bill, as the rate per unit or per kWh. If your tariff has slabs, use the rate for the slab your consumption reaches, since additional usage is charged at that rate.

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