Electrical Power Calculator Formula
Understand the math behind the electrical power calculator. Each variable explained with a worked example.
Formulas Used
Power (V*I)
power_vi = voltage * currentPower (I²R)
power_i2r = pow(current, 2) * resistancePower (V²/R)
power_v2r = pow(voltage, 2) / resistanceVariables
| Variable | Description | Default |
|---|---|---|
voltage | Voltage(V) | 120 |
current | Current(A) | 5 |
resistance | Resistance(Ω) | 24 |
How It Works
Electrical Power
Electrical power is the rate of energy transfer in an electric circuit.
Three Equivalent Forms
P = V * I (voltage times current)
P = I² * R (current squared times resistance)
P = V² / R (voltage squared divided by resistance)
All three yield the same result when V, I, and R satisfy Ohm's law.
Worked Example
A 120 V circuit drawing 5 A through a 24 ohm load.
- 01P = V * I = 120 * 5 = 600 W
- 02P = I² * R = 25 * 24 = 600 W
- 03P = V² / R = 14400 / 24 = 600 W
Frequently Asked Questions
What is the difference between watts and kilowatt-hours?
Watts measure instantaneous power. Kilowatt-hours measure energy consumed over time: 1 kWh = 1000 W used for 1 hour.
How does power relate to heat in a resistor?
All electrical power in a resistor is converted to heat (Joule heating). P = I²R gives the heat dissipation rate.
What is the power of a typical household outlet?
In the US, a 120 V / 15 A outlet can deliver up to 1800 W. A 240 V / 30 A outlet delivers up to 7200 W.
Learn More
Guide
How to Calculate Power Consumption (Watts)
Learn how to calculate electrical power consumption in watts using voltage, current, and resistance. Covers DC circuits, AC apparent vs. real power, and energy cost calculations.
Ready to run the numbers?
Open Electrical Power Calculator