Electric Energy
Understanding electric energy and its common units.
What is Electric Energy?
Electric energy is the total amount of work done or energy consumed by an electrical device over a period of time. It is the capacity to do work and is distinct from electric power, which is the rate at which energy is consumed or produced.
Formulas for Electric Energy
E = P × t
E = V × I × t
E = I² × R × t
E = (V² / R) × t
Where:
• E = Energy (Joules, J or Watt-hours, Wh)
• P = Power (Watts, W)
• t = Time (seconds, s or hours, h)
• V = Voltage (Volts, V)
• I = Current (Amperes, A)
• R = Resistance (Ohms, Ω)
E = V × I × t
E = I² × R × t
E = (V² / R) × t
Where:
• E = Energy (Joules, J or Watt-hours, Wh)
• P = Power (Watts, W)
• t = Time (seconds, s or hours, h)
• V = Voltage (Volts, V)
• I = Current (Amperes, A)
• R = Resistance (Ohms, Ω)
Units of Electric Energy
| Unit | Symbol | Description |
|---|---|---|
| Joule | J | The SI unit of energy. One Joule is equal to one Watt-second. |
| Kilowatt-hour | kWh | Commonly used for billing electricity consumption. 1 kWh = 3.6 × 106 Joules. |
| Watt-hour | Wh | 1 Wh = 3600 Joules. |
Frequently Asked Questions
What is the difference between electric energy and electric power?
Electric energy is the total amount of work done or consumed over time, while electric power is the rate at which that energy is consumed or produced. Think of power as speed and energy as distance traveled.
How is electric energy measured in homes?
Electric energy consumed in homes is typically measured by electricity meters in kilowatt-hours (kWh). This is what you are billed for by your electricity provider.