Ok, thanks for clearing this. You might have large project with different equipments. Here is an example to size generator which covers both motor starting current, running current. Hope this make clear some points.

"Genset Sizing Guidelines

Some conservative rules of thumb for genset sizing include:

1. Oversize genset 20–25% for reserve capacity and for motor starting.

2. Oversize gensets for unbalanced loading or low power factor running loads.

3. Use 1/2 hp per kW for motor loads.

4. For variable frequency drives, oversize the genset by at least 40%.

5. For UPS systems, oversize the genset by 40% for 6 pulse and 15% for 6 pulse with input filters or 12 pulse.

6. Always start the largest motor first when stepping loads.

For basic sizing of a generator system, the following example could be used:

Step 1: Calculate Running Amperes

■Motor loads:

❑200 hp motor . . . . . . . . . . . . . 156A

❑100 hp motor . . . . . . . . . . . . . . 78A

❑60 hp motor . . . . . . . . . . . . . . . 48A

■Lighting load . . . . . . . . . . . . . . . . 68A

■Miscellaneous loads . . . . . . . . . . 95A

■Running amperes. . . . . . . . . . . 445A

Step 2: Calculating Starting Amperes

Using 1.25 Multiplier

■Motor loads:

❑. . . . . . . . . . . . . . . . . . . . . . . . 195A

❑. . . . . . . . . . . . . . . . . . . . . . . . . 98A

❑. . . . . . . . . . . . . . . . . . . . . . . . . 60A

■Lighting load . . . . . . . . . . . . . . . . 68A

■Miscellaneous loads . . . . . . . . . . 95A

■Starting amperes. . . . . . . . . . . 516A

Step 3: Selecting kVA of Generator

■Running kVA =

(445A x 480V x 1.732)/

1000 = 370 kVA

■Starting kVA =

(516A x 480V x 1.732)/

1000 = 428 kVA

Solution

Generator must have a minimum starting capability of 428 kVA and minimum running capability of 370 kVA. Also, please see section “Factors Governing Voltage Drop” on generator loading and reduced voltage starting techniques for motors."

Source:

http://www.zone4info.com/articles/350/a-proper-generator-sizing-guid-line