What is a Kilowatt Hour
The power company charges you for power in kilowatt hours, abbreviated kWh. This guide explains what a kilowatt hour is.
We all know that c are rated in watts, such as a 60 watt light bulb or a 100 watt light bulb. How much you pay for using a light bulb on depends on how long you leave it on for and the wattage rating of the light bulb.
Most power calculation is based on hours. If you turned a 100 Watt light bulb on for 1 hour, then you have used 100 Watt hours. Likewise if you turn the same light bulb on for 2 hours, then you have used 200 Watt hours. Notice that we simply multiply the watts of the light bulb by the number of hours it is left on.
Watt Hours = Watts Used * Hours Used
Item used |
Time used for |
Watt hours Used |
| 100 watt light bulb |
1 hour |
100 |
| 100 watt light bulb |
5 hours |
500 |
| 100 watt light bulb |
24 hours |
2,400 |
| 100 watt light bulb |
24 hours a day for 30 days |
72,000 |
The values in the last column get big fast when you start talking about how much power is used in a month. That is why most power use is measured in kilowatt hours. This simply means "1,000's of Watt hours". Using kilowatt hours, the above table becomes this.
kilowatt Hours Used = (Watts Used * Hours Used) / 1000
Item used |
Time used for |
kilowatt hours Used |
| 100 watt light bulb |
1 hour |
0.1 |
| 100 watt light bulb |
5 hours |
0.5 |
| 100 watt light bulb |
24 hours |
2.4 |
| 100 watt light bulb |
24 hours a day for 30 days |
72 |
This last equation is the one that you should remember when doing kilowatt hour calculations.
kilowatt Hours = (Watts Used * Hours Used) / 1000
If you want to know how much you pay for a kilowatt hour, then you should check our our guides to help you Determine How Much You Pay For Electricity.
Lets do some examples.
Example 1: If you used a 1000 watt curling iron for 1 hour, how many kilowatt hours have you used?
kilowatt Hours = (1000 watts * 1 hour) / 1000 = 1 kWh
Example 2: If you used a 10,000 watt oven for 3 hours, how many kilowatt hours have you used?
kilowatt Hours = (10,000 watts * 3 hours) / 1000 = 30 kWh
We also have a guide to help you learn to Read You Power Meter to Determine Power Usage.
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