Complex sentence: Electrical energy is sold in kilowatt-hours; cost of running equipment is the product of power in kilowatts multiplied by running time in hours and price per kilowatt-hour.
Split into simpler sentences: Electrical energy is sold in kilowatt-hours. The cost of running an electric device is calculated by multiplying the device's power in kilowatts, by the running time in hours, by the price per kilowatt-hour.