Electric Power Calculator

Electric power is the amount of electrical energy consumed or produced per unit time, calculated as voltage times current. The unit is the watt (W).

Enter the voltage (V) and current (I) to instantly get the power consumption of an electronic device. Useful for estimating electricity bills or checking appliance power usage.

For example, at 220 V and 5 A the power consumption is 1,100 W.

Electric Power Calculator Calculation Method

P: power (W), V: voltage (V), I: current (A)

The power (W) is 0 .

About This Calculator

Electric power is the rate at which electrical energy is converted into another form, such as light, heat or motion, and is measured in watts (W). It is the product of voltage and current.

Enter voltage and current to find the power, and combine it with time to find the energy consumed in watt-hours or kWh.

Electrical power is voltage times current, and the same relationship appears in three equivalent forms: P = VI, P = I²R and P = V²/R. A 220 V appliance drawing 5 A uses 1,100 W, and running it for three hours consumes 3.3 kWh. Because resistive loss grows with the square of the current, transmission lines carry power at very high voltage.

Key Formula:P = V × I · P = I²R · E = P × t

Frequently Asked Questions

What is the difference between a watt and a kilowatt-hour?

A watt measures power — energy per second. A kilowatt-hour (kWh) measures energy over time: a 1,000 W appliance running for one hour uses 1 kWh. Electricity is billed in kWh.

How do I estimate an appliance's running cost?

Multiply its wattage by the hours used, divide by 1,000 to get kWh, then multiply by your electricity price per kWh. A 1,500 W heater used 4 hours a day at $0.15/kWh costs about $0.90 per day.

Why do power lines use such high voltage?

For a given power, raising the voltage lowers the current in proportion, and loss is I²R, so the loss falls with the square of the current. That is why long-distance lines run at hundreds of kilovolts.

Why does a motor draw more current at start-up?

A stopped motor has almost no back-EMF, so only the winding resistance limits the current. Inrush can be several times the running current, which is why appliances need a higher start-up rating than their label suggests.

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Sources & last update

2026-10-19