The following formula is used to calculate KWH. In the United States and a few other countries the standard household voltage is. Your electricity company charges by how much electricity you use per kilowatt hour kWh.
For example an appliance that uses 12 amps and runs on North American electricity would use 1440 Watts or 144 kilowatts.
It means that the phase current in amps is calculated by multiplying 1000 by the power in kilowatts dividing the answer by three multiplied by the power factor times the line to neutral voltage RMS In volts. Find the amps rating on your appliance. Suppose a phone battery of power 200 W lasts for 2 hours. Calculating Kilowatt Hours from Amps and Voltage 1.