Electric power is the rate at which an electric circuit transfers electric energy. The SI unit of power is the watt, one joule per second. Electric generators usually produce electric power but can also be supplied by electric batteries. It is generally provided 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 power in kilowatts multiplied by running time in hours. Electric utilities measure ability using an electricity meter, which keeps a total of the electric energy delivered to a customer.