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Generator Load Sizing Calculator
Professional-grade load analysis. Add your equipment, and we'll size the generator including starting surge requirements.
Your Load Items
Running kW
0
Starting kW
0
Recommended kVA
0
Safety Margin
25%
How Generator Sizing Works
To properly size a generator, you need to account for:
- Running load — the continuous power required by all equipment operating simultaneously.
- Starting surge — electric motors draw 3–7× their running current during startup. The generator must handle this momentary peak.
- Safety margin — a 20–25% buffer prevents overloading and extends generator life.
- Future expansion — always plan for an additional 10–15% for future equipment.
Generator kVA = (Total Running kW + Largest Motor Starting Surge kW) × 1.25 ÷ 0.8
Common Starting Surge Multipliers
| Equipment Type | Starting Surge Multiplier |
|---|---|
| Motors (small, capacitor-start) | 3–4× running power |
| Motors (large, across-the-line) | 5–7× running power |
| Pumps / Compressors | 3–5× running power |
| HVAC Systems | 3–5× running power |
| UPS / Lighting | 1.5–2× running power |
| Resistive Loads (heaters) | 1× (no surge) |