How to Calculate Electricity Cost (kWh Cost per Appliance)

By Dr. Ahmed Mortuza Saleque · Updated November 10, 2026 · How we check our content

The short answer

Electricity cost = watts ÷ 1,000 × hours used × price per kWh. A 1,500 W space heater running 5 hours a day uses 7.5 kWh a day. At $0.16 per kWh that costs $1.20 a day, or about $36 over a 30-day month.

Open the Electricity Cost Calculator →

The formula in three steps

Convert watts to kilowatts: divide the appliance's wattage by 1,000. A 1,500 W heater is 1.5 kW.
Multiply by the hours it runs to get kilowatt-hours (kWh). 1.5 kW × 5 hours = 7.5 kWh.
Multiply the kWh by your price per kWh. 7.5 kWh × $0.16 = $1.20.

To skip the arithmetic, enter the wattage, hours and price into the electricity cost calculator.

Where to find the wattage

Look for the rating label on the back or underside of the appliance, or in its manual. It lists the power in watts (W) or kilowatts (kW).

If the label only shows amps, multiply amps by the supply voltage: a 12 A appliance on a 120 V circuit draws 12 × 120 = 1,440 W. The label shows the maximum draw, so appliances that cycle on and off, such as fridges, use less on average. A plug-in energy meter measures the real figure.

Where to find your price per kWh

Your electricity bill lists the energy charge per kWh. If it only shows totals, divide the energy part of the bill by the kWh used: $142.50 for 950 kWh is $0.15 per kWh. Leave out fixed monthly service charges, which you pay however much you use.

On a time-of-use plan the price changes through the day, so use the rate for the hours the appliance actually runs.

What common appliances cost to run

Typical wattages and usage, at $0.16 per kWh over a 30-day month. Your appliance and price will differ.

Appliance	Power	Use per day	kWh per month	Cost per month
LED bulb	10 W	5 h	1.5	$0.24
Laptop	60 W	8 h	14.4	$2.30
TV	100 W	4 h	12	$1.92
Microwave	1,000 W	15 min	7.5	$1.20
Washing machine	500 W	1 h	15	$2.40
Refrigerator (average draw)	150 W	8 h running	36	$5.76
Electric dryer	3,000 W	1 h	90	$14.40
Space heater	1,500 W	5 h	225	$36.00
Window air conditioner	1,000 W	8 h	240	$38.40
Electric car (30 miles a day)	0.3 kWh per mile	9 kWh	270	$43.20

Heating and cooling dominate most bills because they combine high power with long running hours. Lighting and electronics cost far less than people expect.

Standby power adds up

A device drawing 5 W on standby all year uses 5 × 24 × 365 ÷ 1,000 = 43.8 kWh, about $7 a year at $0.16 per kWh. Ten such devices cost about $70 a year for doing nothing. A switched power strip removes that cost.

From one appliance to the whole bill

Add up the monthly kWh of each appliance to estimate your total use, then multiply by your rate and add the fixed charges. The electricity bill calculator does this for a list of appliances. If you are thinking about generating your own power, the solar panel guide shows how many panels cover a given bill.

Common questions

How do I convert watts to kWh?

Multiply watts by hours and divide by 1,000. A 100 W device running for 10 hours uses 100 × 10 ÷ 1,000 = 1 kWh.

How much does it cost to run a 1,000 W appliance for one hour?

It uses exactly 1 kWh, so it costs your price per kWh: $0.16 at 16 cents per kWh.

What does it cost to leave a 100 W bulb on for 24 hours?

100 W × 24 h = 2.4 kWh, which is about $0.38 at $0.16 per kWh. An equivalent 14 W LED would cost about 5 cents.

What is a kilowatt-hour?

A unit of energy: the amount used by a 1,000 W appliance in one hour. It is what electricity meters count and what bills charge for.

Calculators for this article

Sources

U.S. EIA – Electric Power Monthly (average electricity prices)