While both kVA and kW are units of measure, kVA is a kilo volt amperes and kW is a kilowatt. Both the kVA and the kW are units used to express power.
kVA is known as the apparent power of an electrical system or of a particular circuit. In direct current circuits the kVA is equal to the kW because the current and the voltages do not get out of phase. However, "real power" and "apparent power" differ in their alternating current circuits so kW is the amount of actual power that does valid work where only a fraction of kVA is available and accessible to do work while the rest is in excess in the current.
The relationship between kVA, kW and the power factor is described mathematically as: kW = kVA x power factor; kVa = kW/power factor; and power factor = kW/kVA. In DC circuits, there is no difference between the kVA and the kW because of the power factor. The power factor leads or lags depending on the way that the load shifts the phase of the current compared to the phase of the voltage. This creates a unity in the DC circuits. In AC circuits, voltage and current may get out of phase leading to a difference in kW and kVA that will be based on the power factor (or how much leading or lagging occurs).