KW is a unit of power. KVA is a calculation, equal to amperage multiplied by voltage. The two are the same when no reactive currents are present. There are two types of reactive currents: Inductive and capacitive. Motors and transformers are two of the most common sources of inductive currents. Capacitors create capacitive currents.
The only energy transfer inherent in reactive currents are the I square R losses in the conductors. Utilities hate reactive power in their power lines because the I square R losses cost them money. They sometimes penalize users with large motor loads because motors create so much reactive currents. Long ago, utilities would create capacitive currents using 'over excited (field windings were deliberately over driven)' synchronous motors to create capacitive currents, which reduced the inductive currents in the power lines.
Reactive power is actually power that is echoed back and forth between source and load with no net transfer of power actually taking place.
Doug S, I'd suggest investing in a 3 phase power meter. Takes only a few seconds to connect it and it will show you the actual load. I have a handheld model laying around in my shop somewhere. Must be older than I am. It's about the size of a large clamp-on meter but has 3 leads coming out of it to connect to the lines.