Appliance Electricity Cost Calculator

Calculate your appliance's cost

How the calculation works

Three steps, all of which you can check with a phone calculator:

• ✓Units = watts × hours ÷ 1000 — one unit on your bill is one kilowatt sustained for one hour. A 100W appliance run 4 hours a day uses 0.4 units that day.
• ✓A month is roughly 30 days — so the monthly figure is the daily units scaled up: 12 units a month for that same appliance.
• ✓Priced at your marginal rate — not your average rate. Indian residential tariffs are telescopic, so whatever you add on top of your existing usage lands on your highest slab. That rate already includes the fuel cost adjustment and electricity duty.

Takeaway: the whole calculation is two multiplications and a tariff lookup — nothing here is a black box.

Wattage decides the rate, hours decide the bill

A high-wattage appliance used briefly can cost less than a low-wattage one left running all day. Units are watts times hours, so usage pattern matters as much as the number printed on the appliance:

All rows priced at TNEB's marginal rate for illustration — use the calculator above with your own DISCOM.

Notice the 2000W water heater run half an hour a day uses more than the 10W bulb run five hours a day, but not by as much as the wattage gap alone suggests — because the bulb's hours partly make up for its lower draw. This is why a wattage figure alone, without hours, tells you very little.

Takeaway: always multiply by hours before comparing two appliances — wattage alone is not a cost ranking.

The cost of devices you never switch off

Phones, set-top boxes, routers, chargers left plugged in, and appliances with a standby light all draw a small current around the clock. A single device drawing a steady 5W, 24 hours a day, every day of the month, comes to 3.6 units — and a typical home has several such devices running simultaneously, not one.

Unlike a washing machine or geyser, standby draw is invisible in daily life — nobody notices a router that is always on, because it is supposed to always be on. That is exactly why it is worth checking: it is the one category of load this calculator can price but that you cannot time with a stopwatch, since the “hours per day” is simply 24. Our phantom load checker is built specifically for tallying several such devices at once.

Takeaway: small wattage multiplied by 720 hours a month is not negligible — check what is always plugged in, not just what you turn on.

Mistakes that throw the number off

• ✕Reading VA instead of W — some labels print apparent power (volt-amps) rather than real power (watts). For a purely resistive appliance (a heater, an iron) the two are close; for a motor or electronics they can differ meaningfully.
• ✕Using the rated maximum, not typical draw — a kettle or iron cycles its heating element on and off once it reaches temperature; its nameplate wattage is the peak, not the sustained average.
• ✕Entering hours switched on rather than hours actually drawing power — a washing machine running a 45-minute cycle is not drawing its full wattage for the whole 45 minutes; a TV left on mute while you leave the room still counts as on.
• ✕Treating units as rupees — this tool's output is kWh; the ₹ figure comes from multiplying by your DISCOM's marginal rate, which the calculator does for you.

Takeaway: a wrong wattage or wrong hours figure is the usual cause of a result that looks off — not the formula.

When a dedicated calculator gives a better answer

This tool treats every appliance as a constant wattage for however many hours you enter, which is accurate for simple resistive loads but understates or overstates a few categories with their own behaviour:

• →Air conditioners cycle their compressor on and off rather than running flat out — our AC running cost calculator models that duty cycle from tonnage and star rating instead of a flat wattage.
• →Refrigerators run continuously but cycle their compressor too, and the BEE label already states an annual kWh figure measured in a lab — our fridge cost calculator uses that label figure directly rather than a wattage guess.
• →Ceiling fans have their own calculator with speed-setting presets, since running one at a lower speed draws noticeably less than nameplate wattage — see our ceiling fan cost calculator.
• →EV charging is a much larger, sustained load with its own charger-efficiency considerations — handled by our EV charging cost calculator.

Takeaway: use this tool for everything without a dedicated calculator — irons, mixers, washing machines, routers, chargers, lighting — and the specialised tools where one exists.

Typical appliance wattage — reference only

These are commonly published ranges to help you sanity-check a figure — always use the wattage printed on your specific appliance for an accurate calculation.

Related calculators

Frequently asked questions