Construction Site preset for the Generator Load Calculator: mixed tools. Pre-filled inputs Running Load W 25000, Starting Load W 55000, Power Factor 0.8.
Pre-filled Inputs
Exact preset input values
Running Load W
25000
Starting Load W
55000
Power Factor
0.8
Voltage
400
Phases
3
Governing Formulas
Engineering formulas used by this calculator
Expression
Result
P_run = Σ (running watts × qty)
Total running load (W)
P_surge = P_run + max(starting − running)
Peak surge (W)
kW = max(P_run × 1.25, P_surge × 1.10) / 1000
Recommended kW
kVA = kW / power factor
Apparent power (kVA)
Frequently Asked Questions
How do I size a standby generator?
Total the running watts of every connected load, add the largest motor starting surge, then take the greater of running load × 1.25 or surge × 1.10.
Why does motor starting surge matter?
Motors draw several times their running current at start-up, so the sizing uses the largest single starting delta rather than the sum of all surges.
What power factor should I use for kVA sizing?
Use the nameplate power factor of the connected equipment; motor-heavy loads commonly run 0.8, which raises the apparent power in kVA for the same kW.