Kilojoules to Kilowatt-hours conversion

How to convert kilojoules to kilowatt-hours?

To convert kilojoules (kJ) to kilowatt-hours (kWh), you need to understand the relationship between these units. The conversion factor is based on the definition of a kilowatt-hour and a joule.

1 kilowatt-hour (kWh) is equal to 3,600,000 joules (J) because there are 3,600 seconds in an hour and 1 watt is equal to 1 joule per second (J/s). Therefore: $1 \text{kWh} = 3,600,000 \text{J}$

Since 1 kilojoule (kJ) is 1,000 joules (J), you can use this fact to derive the conversion factor.

To convert from kilojoules to kilowatt-hours: $1 \text{kJ} = 1,000 \text{J}$ $1 \text{kWh} = 3,600,000 \text{J}$

Thus, the conversion is: $1 \text{kJ} \times \frac{1 \text{kWh}}{3,600,000 \text{J}} = \frac{1,000 \text{J}}{3,600,000 \text{J}} = \frac{1}{3,600} \text{kWh}$

So, $1 \text{kJ} = \frac{1}{3,600} \text{kWh}$ $1 \text{kJ} \approx 0.000278 \text{kWh}$

Examples for Different Quantities of Kilojoules

• 50 kJ to kWh: $50 \text{kJ} = 50 \times 0.000278 \text{kWh}$ $50 \text{kJ} ≈ 0.0139 \text{kWh}$

• 200 kJ to kWh: $200 \text{kJ} = 200 \times 0.000278 \text{kWh}$ $200 \text{kJ} ≈ 0.0556 \text{kWh}$

• 1,000 kJ to kWh: $1,000 \text{kJ} = 1,000 \times 0.000278 \text{kWh}$ $1,000 \text{kJ} ≈ 0.278 \text{kWh}$

Real-World Examples

1. Daily Energy Use of an LED Bulb:

   • Assume a 10-watt LED bulb is used for 10 hours.
   • Energy consumption in kWh: $10 \text{W} \times 10 \text{hr} = 0.1 \text{kWh}$
   • Converting to kJ: $0.1 \text{kWh} \times 3,600 \text{kJ/kWh} = 360 \text{kJ}$

2. Energy in Food:

   • A medium-sized apple roughly contains about 52 kcal.
   • 1 kcal ≈ 4.184 kJ, so: $52 \text{kcal} \times 4.184 \text{kJ/kcal} ≈ 217.568 \text{kJ}$

3. Physical Activity:

   • Running at a moderate pace can burn about 10 kJ per minute.
   • For a 30-minute run: $10 \text{kJ/min} \times 30 \text{min} = 300 \text{kJ}$
   • In kWh: $300 \text{kJ} \times 0.000278 \approx 0.0834 \text{kWh}$

By understanding these conversions and examples, you can get a sense of how energy in kilojoules relates to common activities and electrical usage in kilowatt-hours.