Electrical Energy Calculator Formula
Understand the math behind the electrical energy calculator. Each variable explained with a worked example.
Formulas Used
Energy (kWh)
energy_kwh = power_watts * time_hours / 1000Energy (Joules)
energy_joules = power_watts * time_hours * 3600Variables
| Variable | Description | Default |
|---|---|---|
power_watts | Power(W) | 100 |
time_hours | Time(hours) | 5 |
How It Works
Electrical Energy
Electrical energy is power consumed over a period of time.
Formula
E = P * t
In practical units: kWh = W * hours / 1000. In SI units: Joules = Watts * seconds.
Worked Example
A 100 W light bulb running for 5 hours.
power_watts = 100time_hours = 5
- 01E = P * t
- 02E = 100 * 5 = 500 Wh
- 03E = 0.5 kWh
- 04E = 100 * 5 * 3600 = 1,800,000 J
Frequently Asked Questions
What is a kilowatt-hour?
A kWh is the energy consumed by a 1000 W appliance running for 1 hour. It is the standard unit on electricity bills.
How much does 1 kWh cost?
Varies by location and provider. In the US, the average is roughly $0.12 to $0.30 per kWh.
How do I calculate my electricity bill?
Sum the kWh used by each appliance (power * hours / 1000), then multiply total kWh by your rate per kWh.
Ready to run the numbers?
Open Electrical Energy Calculator