<P> Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit . The SI unit of power is the watt, one joule per second . </P> <P> Electric power is usually produced by electric generators, but can also be supplied by sources such as electric batteries . It is usually supplied to businesses and homes by the electric power industry through an electric power grid . Electric power is usually sold by the kilowatt hour (3.6 MJ) which is the product of the power in kilowatts multiplied by running time in hours . Electric utilities measure power using an electricity meter, which keeps a running total of the electric energy delivered to a customer . </P> <P> Electrical power provides a low entropy form of energy and can be carried long distances and converted into other forms of energy such as motion, light or heat with high energy efficiency . </P>

Unit of electric power may also be expressed as