Watts and Volt Amps as Explained by ACUPWR USA: The Voltage Transformer Company

When you look on the back of an electrical appliance, you’ll notice two measurements; one for wattage, and one for volt amps (VA). These values represent the amount of power that an appliance needs to run. They also measure the power that the device is drawing, or consuming, from the electrical grid.

Both wattage and VA are useful in different ways. For the electric company, wattage—specifically kilo-watts—determine how much to bill a customer each month. It also determines the amount of electricity needed for the product to operate continuously. For example, if a large industrial machine requiring 3,000 watts is attached to a wall outlet that can only deliver 2,000 watts, there will most certainly be an overload and possible fire. 

Meanwhile, VA is used for determining the type of wiring that is necessary for the device. Large industrial equipment will have a very high VA rating and therefore need thick, heavy duty wiring—enough to carry the large amount of current that needs to flow into, say, a huge central air conditioning unit.  

Wattage and VA represent power in different ways. Wattage represents real (or true) power—the actual power that is taken from the wall outlet (or, really, the electricity company). VA represents apparent power, which is the power drawn from the wall but also factoring in wasted power that is caused by various conditions that occur in the AC line. This wasted energy is called reactive power. The ratio of real power and reactive power is something called power factor (PF): a number that ranges from .55 to 1.  

The formula for measuring VA is: 

• VA = Volts x Amps

The formula for measuring wattage is:

• Wattage = Volts x Amps x PF

With ACUPWR transformers the VA and wattage will always be identical because the power factor is 1, which means that there is no wasted energy coming from our voltage transformers and converters.