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How To Calculate Electricity Usage

Updated on August 13, 2013

Are you looking to find the electricity cost of a device or home appliance? The method to calculate electricity consumption and electricity cost of a device is rather simple, simply follow this guide.

The Easy Way

The easiest way is to use an electricity usage calculator online. It will do all the calculations for you. Take a look at, it provides you with far more information about electricity usage and prices compared to following the formula below. Energy Use Calculator also offers advice on reducing energy costs and basic information about a large selection of devices, such as the average wattage of devices and the regular time of operation.

Visit to use this simple web calculator for free to find out energy consumption and cost of any device!
Visit to use this simple web calculator for free to find out energy consumption and cost of any device!

The Hard Way

The hard way is to do all the calculations yourself, follow the steps below.

Step #1: Take the device you want to calculate the energy cost for and check the label. It should tell you up to how many watts the device will use. For example a regular CFL lightbulb will use between 13 and 15 watts per hour.

Step #2: Take the number you get in watts and divide it by 1000. This is done to convert to kilowatts. In our example we will take a CFL light bulb which uses 14 watts and divide it by 1000.

Formula to convert to kilowatts: watts / 1000 = kW

Our example: 14 / 1000 = 0.014

Step #3: Now you will need to multiply the kilowatts by the number of hours the device is being used for. For example let's say our CFL Lightbulb is being used for 10 hours.

Formula to obtain kilowatt-hours: kW * hours = kWh

Our example: 0.014 * 10 = 0.14

Step #4: To find the cost to operate the device you now need to multiply kWh by the cost per a kWh. The cost per a kWh varies significantly depending where you live, you should check your energy bill to determine how much you pay. In North America the average is roughly 10 cents per a kWh.

Formula to find the electricity cost: kWh * price per a kWh = cost to run the device

Our example: 0.14 * $0.10 = $0.014

This means that a CFL light bulb using 14 watts per an hour for 10 hours at 10 cents per a kWh will cost $0.014 to operate or 1.4 cents. If you run this device every day for 10 hours for one year, multiply the 1.4 cents by 365 days and you will get 511 cents which is $5.11.

Common Devices and How Much Energy They Use

CFL Light Bulb
Incandescent Light Bulb
LED Light Bulb
LED/LCD Display
Desktop Computer
Laptop (charging)
Game Console
Coffee Machine


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