MAXScanner calculator widget

Generator Sizing Calculator — kW, kVA & Motor Starting Load

Editable live calculator

Change any input — the result updates immediately

No hidden assumptions. Inputs, units and the working stay visible so you can check the calculation.

Simultaneous running load (kW) Real power expected to be on at the same time.Running-load power factor Use a measured or design load PF; must be >0 and ≤1.Largest motor running load (kVA) This motor running kVA must already be included in the total running load. Use 0 when not applicable.Motor starting kVA multiple Prefer motor/starter/OEM study data. Minimum 1×.Spare capacity / growth (%) Deliberate planning margin, separate from site derating.Verified genset derating factor Use 1.0 when no manufacturer derating applies. Range >0 to 1.Generator line voltage (V) Line-to-line voltage for three-phase.Output phase

Calculated result

151.32 kVA minimum planning size

Running load: 50 kVA (40 kW at PF 0.8)

Motor-start scenario: 125 kVA

Governing case: Motor-start scenario

Equivalent real power at entered PF: 121.05 kW

Approximate rated current at 415 V 3φ: 210.51 A

Show the working

1. Running kVA = 40 kW ÷ 0.8 = 50 kVA.
2. Other running load = 50 − 15 = 35 kVA.
3. Motor starting demand = 15 × 6 = 90 kVA.
4. Starting scenario = 35 + 90 = 125 kVA.
5. Governing demand = max(50, 125) = 125 kVA.
6. Required size = 125 × 1.15 ÷ 0.95 = 151.32 kVA.

More actions

Shared links reopen these inputs. Recent and saved calculations stay in this browser unless you clear site data.