Start with the load, not the generator
Generator sizing begins with the equipment that must run during an outage. Record running power, motor starting requirements, phase and whether loads start simultaneously.
kW and kVA are not interchangeable
Generator sets are commonly marketed in kVA. The relationship to usable kW depends on power factor and the generator specification. Use the manufacturer rating and a qualified electrical assessment for final selection.
Allow for motor starting
Pumps, compressors and refrigeration can draw substantially more current while starting. This is one reason commercial generator selection should not be based only on the sum of nameplate running watts.