Electrical Power Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
Electrical power is calculated with P = U × I, where U is voltage in volts and I is current in amps. Under a voltage of 230 V with a current of 5 A, the power is 1,150 W.
Explanation
Electrical power (in watts) measures the amount of energy consumed or produced per unit of time in a circuit. It's calculated by multiplying voltage (U, in volts) by current (I, in amps): P = U × I. This formula, valid for DC and, as a first approximation, for resistive AC circuits, lets you estimate the power actually consumed by an electrical appliance if you know the current it draws under mains voltage (230 V in France). It's also the basis for sizing a fuse or an electrical installation: knowing an appliance's power lets you derive the current it draws (I = P ÷ U), and therefore the protection rating needed. For the voltage of a resistive circuit from its resistance, see our Ohm's law calculator.
Example: a voltage of 230 V, a current of 5 A
Inputs
Voltage: 230 V. Current: 5 A.
Calculation
Power = voltage × current = 230 × 5 = 1,150.
Result
The electrical power consumed is 1,150 W, or 1.15 kW.
Frequently asked questions
How do I convert watts to kilowatts?
Divide the value in watts by 1,000: 1,150 W equals 1.15 kW. It's this unit (the kilowatt-hour, kWh, once multiplied by a duration) that shows up on an electricity bill.
Does this formula apply to household AC current?
For a purely resistive load (like a heater or an incandescent bulb), yes, directly. For appliances with a motor or an electronic power supply (a power factor different from 1), the real power can differ slightly from this simple U × I product — a useful detail in electrical engineering, but negligible for most everyday uses.
How do I find the current from the power?
By rearranging the formula: current = power ÷ voltage (I = P ÷ U). For example, a 1,150 W appliance plugged into 230 V draws 1,150 ÷ 230 = 5 A.