Here is where we all get into trouble.

How to convert VA to Watts and KVA to Kilowatts

Basics

Since watts is volts times amps, what is VA? VA (or volt-amps) is also volts times amps, the concept however has been extended to AC power. For DC current

VA = Watts (DC current).

In AC if the volts and amps are in phase (for example a resistive load) then the equation is also

VA=Watts (resistive load)

where V is the RMS voltage and A the RMS amperage.

In AC the volts and amps are not always in phase (meaning that the peak of the voltage curve is does not happen at the peak of the current curve). So in AC, if the volts and amps are not precisely in phase you have to calculate the watts by multiplying the volts times the amps at each moment in time and take the average over time. The ratio between the VA (i.e. rms volts time rms amps) and Watts is called the power factor PF.

VA·PF = Watts (any load, including inductive loads)

In other words, volt-amps x power factor = watts. Similarly, KVA*PF = KW,
Or kilovolt-amps times power factor equals kilowatts.

When you want to know how much the electricity is costing you, you use watts. When you are specifying equipment loads, fuses, and wiring sizes you use the VA, or the rms voltage and rms amperage. This is because VA considers the peak of both current and voltage, without taking into account if they happen at the same time or not

Finding the Power Factor

How do you find the power factor? This isn't easy. For computer power supplies and other supplies that are power factor corrected the power factor is usually over 90%. For high power motors under heavy load the power factor can be as low as 35%.

Industry standard rule-of-thumb is that you plan for a power factor of 60%, which somebody came up with as a kind of average power factor.