How do you calculate load in KW?

You have to know 2 things in order to perform the calculation. You will need to know the power (KW) and either the amps or the voltage. If you know voltage you can determine amps and if you know amps you can determine voltage. However with solely the KW you do not have enough information to calculate either. Here is the formula:

1 Phase: KW = (E x I x pf)/ 1000

3 Phase: KW = (1.732 x E x I x pf)/1000

Where E is voltage, I is current, and pf is Power Factor