Wattage is a measure of electrical power, expressed in watts. It’s the product of one ampere (1A) of current multiplied by one volt (1V) across an electrical circuit, and is used to calculate the total amount of energy being supplied or used by a system. Wattage can be used to measure energy output from electrical appliances such as lamps, fans and vacuum cleaners, or it can be used to measure the amount of electricity consumed by electronic components in circuits. Additionally, wattage is essential for calculating the overall efficiency of mechanical devices such as engines and dynamos since it shows how much useful work they can produce with their total input power. The higher the number of watts produced, the more efficient the device is at converting energy into work – and vice versa.