FAQ

What is the difference between VA and W? Explaining the use of different electrical power units

Category
Specification of Power Supply

VA (volt-amperes) and W (watts) are used as units of electric power. In some cases, the prefix kVA (kilovolt-ampere) or kW (kilowatt) is also used.
Why are there two units of electrical power, VA and W?
Each unit has a difference in the amount of electrical power it represents.

VA: Apparent power (Real or true power + reactive power)
W: Active power or real power

For more information about active power, reactive power, and apparent power, see "Difference between DC power and AC power".
Please see https://www.matsusada.com/column/dc_and_ac.html
For more information on effective power, please refer to "Differences between DC power and AC power" at .

We use VA as the output unit for AC power sources and W as the output unit for DC power supplies, etc.

Conversion of units

To convert VA to W, you need to know the power factor of the AC power load.
For example, if the power factor is 100%, reactive power is zero and apparent power = active power.
AC loads with zero reactive power are those with matching voltage and current waveforms, such as electric heating loads like incandescent light bulbs, irons, and electric kettles. On the other hand, devices that contain inductivity, such as motors, have a power factor of about 0.5 to 0.8.
If the equipment has a power factor correction (PFC) circuit, the power factor will be 0.8 to 0.9 or higher.