Electrical power Calculator: measuring notes and method
Use electrical input values
Use the voltage across the load and current through it. A supply’s total output is not necessarily the power consumed by one connected device.
CHECK A PRACTICAL EXAMPLE
Check the scope of voltage × current
Use an ideal 12 V DC load for this arithmetic comparison.
1 A current
- Electrical power
- 12 W
- Power
- 0.012 kW
2 A current
- Electrical power
- 24 W
- Power
- 0.024 kW
At fixed voltage, doubling current doubles electrical input power. The simple model does not include reactive AC power factor or three-phase systems.
Fixed comparison in metric units. Values are illustrative unless linked to a recorded project; changing the calculator above does not change this example.
Formula
Power (W) = voltage (V) × current (A).
Product reference: Fluke electrical glossary
Worked example
Illustrative values match Reset example and stay fixed when you edit the calculator.
Starting-value worked example
- Voltage
- 230 V
- Current
- 10 A
Electrical power: 2,300 W
Follow the calculation
- Power = 230 V × 10 A = 2,300 W.
- Divide watts by 1,000 to obtain 2.3 kW under this model.
Example: a low-voltage DC load
For a steady 12 V DC supply and 5 A current, P = 12 × 5 = 60 W = 0.06 kW. Use the voltage at the load; voltage drop in long cables is not included.
Why power factor matters for AC
For single-phase AC, real power is RMS voltage × RMS current × true power factor. At 230 V, 10 A and power factor 0.8, apparent power is 2,300 VA but real power is 1,840 W. This calculator has no power-factor input and would show 2,300 W, so it must not be used as the real-power answer for that load.
Power is different from energy
Kilowatts describe power at a moment; kilowatt-hours describe energy over time. A constant 2.3 kW load running for two hours consumes 4.6 kWh. Use the energy-use calculator for operating-time estimates.
Reviewed 19 October 2026. How calculations are checked · Report a correction