Mobile & Electronics

Device Running Cost Calculator

What one appliance costs you a month, so you can decide whether to run it, replace it, or use it differently.

6 inputs Free, no sign-up

Your figures

The rating plate figure. For anything thermostatic, this is the power while it is actually running.

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

Most appliances cost less to run than people expect, and a few cost far more. A ceiling fan for twelve hours a day is a couple of hundred rupees a month; a water heater for one hour a day is nearly twice that. The only way to know which is which is to work it out.

This is the calculation for a decision: whether an old appliance is worth replacing, whether a habit is worth changing, or whether something you were told is expensive actually is.

How to use this calculator

  1. Find the wattage. It is on the rating plate, the adapter, or the back of the unit.
  2. Enter the hours it genuinely runs a day. For a fridge or an air conditioner, that is compressor running time, not switched-on time.
  3. Enter your rate per unit from your bill.
  4. Compare two appliances by running the numbers twice — the difference is what a replacement would save.

The formula

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

To value a replacement, work out both appliances and subtract. An old 80 W fan against a 35 W one saves 45 W for every hour both would run, and the payback period is the price difference divided by the monthly saving.

SymbolMeaningUnit
P Appliance wattage W
Hours Actual running hours h
Rate Your tariff per unit Rs/kWh

Worked example

A 150 W desktop computer, 6 hours a day, at ₹8.50 a unit:

Units a day  = 150 x 6 / 1000 = 0.9
Cost a month = 0.9 x 30 x 8.50 = Rs 229.50
Cost a year                     = Rs 2,754

Notes and limits

  • No wattages are supplied here for any appliance. Devices of the same description vary by a factor of several, so the figure has to come from your own rating plate.
  • Thermostatic appliances — fridges, air conditioners, geysers — cycle on and off. Using switched-on hours instead of running hours overstates their cost substantially.
  • Appliances draw less than their rating most of the time. The rating is the ceiling.
  • The saving from a replacement is the difference between two of these calculations, not the new appliance's own cost.
  • This is the device's energy cost. A bill adds fixed charges, slabs, fuel adjustment and duty.

What this calculation assumes

  • The appliance draws the wattage entered while it runs.
  • Hours are running hours, not switched-on hours, for anything that cycles.
  • The figure is this appliance's energy cost, not a bill.

Frequently asked questions

How much does it cost to run an appliance per month?

Multiply its wattage by the hours a day and the days a month, divide by 1,000 for units, and multiply by your rate. The wattage has to come from your own appliance, since two with the same description can differ by a factor of several.

Is it cheaper to leave an appliance on or switch it off?

For almost everything, off. The exception is anything with a large start-up cost or a thermal cycle, where brief off periods do not save. Standby power is small per hour but runs continuously, so it is worth knowing.

How do I work out whether replacing an old appliance pays?

Work out the monthly cost of both, subtract to get the saving, and divide the price difference by that saving. The result is how many months the replacement takes to pay for itself.

Why does my fridge cost less than its wattage suggests?

Because the compressor runs only part of the time. A fridge rated 150 W might run its compressor a third of the day, so its real consumption is roughly a third of what continuous running would give.

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