Kilowatt-Hour (kWh)
A kilowatt-hour (kWh) is a unit of energy that is commonly used to measure electrical energy consumption. It represents the amount of energy consumed by a device with a power rating of 1 kilowatt (kW) operating for 1 hour.
In simpler terms, 1 kWh is the energy used when a 1,000-watt device runs for one hour.
Relation Between Kilowatt-Hour (kWh) and Joule (J)
The joule (J) is the SI unit of energy, and the kilowatt-hour (kWh) is a larger unit used in the context of electrical energy, commonly in household or industrial settings.
To convert kilowatt-hours to joules, we use the following relationship:
1 kWh=1 kW×1 hour
Since:
- 1 kW=1,000 W
- 1 hour=3,600 seconds
Therefore:
1 kWh=1,000 W×3,600 s=3,600,000 J
Thus,
1 kWh=3.6×106 J
How to Calculate Energy in kWh
To calculate energy in kilowatt-hours (kWh), you can use the formula:
Energy (kWh)=Power (W)×Time (hours)/1,000
Where:
- Power (W) is the power of the device in watts (W).
- Time (hours) is the duration of usage in hours.
Example:
If you have a device with a power consumption of 500 watts and it runs for 3 hours, the energy consumed in kWh is:
Energy (kWh)=500 W×3 hours/1,000=1.5 kWh
This means the device consumes 1.5 kWh of energy in 3 hours.
Summary:
- Kilowatt-hour (kWh) is a unit of energy, primarily used to measure electricity consumption.
- 1 kWh = 3.6 million joules (3.6 × 10⁶ J).
- The energy consumed in kWh can be calculated by the formula: Energy (kWh)=Power (W)×Time (hours)/1,000