Electrical Power

Energy is transferred at the rate of one joule per second by a one watt device. High powered devices are rated in kilowatts which means a thousand watts.

We can find the power rating in watts by multiplying the current and the voltage used by an electrical device.

To calculate energy used in joules we multiply watts and time in seconds. However, for more powerful devices, to calculate energy in kilowatt-hours we multiply kilowatts by the time in hours.

We can calculate the cost of using electricity if we know the cost of a kilowatt-hour (unit) of electricity.