How Much Is a kWh?

••• romaset/iStock/GettyImages

A kWh, or kilowatt-hour, is a measure of electricity usage. Most utilities base their billing on the number of kWh consumed during the billing period.

Significance

Understanding kWh calculations allows you to control your electric bill. You can calculate the cost of operating any electrical device.

Considerations

One kilowatt is 1,000 watts. Running a device that consumes 1,000 watts for one hour results in the consumption of one kilowatt-hour, or kWh, of electricity. By the same token, one hour of running several devices whose combined power use is 1,000 watts--for example, 10 100-watt light bulbs--also consumes one kWh.

Calculating Power Consumption

Each type of electrical device in your home is rated for power consumption by the manufacturer. A compact fluorescent light bulb might, for example, be rated at 13 watts, while an electric range might be 10,000 watts. You can find this information on the packaging, in the owner's manual or printed on the device label. Dividing the wattage rating by 1,000 gives the power consumption in kilowatts. You then multiply this value by the number of hours of operation to obtain the number of kWh consumed.

Example

You want to find out how much it costs per month to operate your outdoor security lighting for eight hours each night. You have four lighting units, each of which has a 75-watt bulb. A kWh costs 42 cents in your area. Four bulbs at 75 watts each equals 300 watts, or 0.3 kilowatts. Multiplying by eight hours gives 2.4 kWh per night. For a 30-day month, this equals 72 kWh. At 42 cents per kWh, your monthly cost equals $30.24, or just over a dollar a day.

Fun Fact

Manufacturers advertise the cost-savings from using compact fluorescent lamps (CFLs) by basing their claims on the kWh these lamps consume as compared to incandescent lamps of similar brightness. Because CFLs produce more light with less electricity, operating them for a given period consumes fewer kWh and therefore saves money.

Related Articles

How to Calculate kWh for Lighting
How to Calculate Battery Watt-Hours
How to Convert Kilowatts to Kilowatt Hours
How to Convert kWh to kBtu
How to Measure Electric Motor Torque
How to Convert HP to BTU/hr
Energizer Watt-Hour Battery Specs
How to Calculate KVA From The Electric Bill
How to Compare LED Light Output to Incandescent Bulbs
How to Calculate Efficacy
Facts About Turning Off Lights to Save Energy
Watt Hour Vs. Amp Hour
How to Convert Horsepower to kWh
What Is the Relationship Between Amps & AH?
How to Calculate Lighting Load
How to Calculate Electrical Capacity
Lumens Vs. Wattage Vs. Candlepower
How to Convert Therms to KWH
How to Calculate Lumens Per Watt
How to Calculate the Electrical Consumption of a Motor

Dont Go!

We Have More Great Sciencing Articles!