By HuaQuan Engineering TeamPublished: 2026-07-17

Quick Answer

For mobile vs stationary generators, typical generator sizes range from N/A. The critical sizing factor is mobility requirements influence frame design and fuel system. Always calculate both running kW and starting kVA, apply appropriate diversity factors, and add 20% growth margin for future expansion.

Generator Sizing for Mobile vs Stationary Generators — Complete Guide (2026)

Proper generator sizing for mobile vs stationary generators is essential for reliable power. This comprehensive guide covers everything you need to know to select the right generator size.

Power Requirements for Mobile vs Stationary Generators

Mobile vs Stationary Generators applications have specific power requirements that must be understood before sizing. The load profile typically includes a mix of resistive and inductive loads with varying duty cycles.

Key Concepts for Mobile vs Stationary Generators

Understanding mobile vs stationary generators is fundamental to generator sizing. This guide explains the differences, tradeoffs, and selection criteria to help you make the right choice.

Sizing Methodology for Mobile vs Stationary Generators

Step 1: Complete a detailed load survey. Step 2: Separate running loads from starting loads. Step 3: Calculate total running kW with diversity factor. Step 4: Add the largest motor starting kVA. Step 5: Apply environmental de-rating factors. Step 6: Add growth margin and select standard size.

ParameterValueNotes
ApplicationMobile vs Stationary GeneratorsSpecific sizing considerations apply
Typical SizeN/AVaries with specific requirements
Diversity Factor0.6-0.9Depends on load coincidence
Growth Margin20%Standard for new installations
Phase1 or 3Based on load types
Frequency50 or 60 HzRegion dependent
Load Component% of TotalStarting Factor
Motor Loads40-60%3-7x
Resistive Loads20-30%1x
Lighting10-20%1x
Electronics/IT5-15%1-2x

Key Takeaways

Summary

Proper generator sizing is the foundation of reliable backup power. By calculating both steady-state running loads and transient starting requirements, applying appropriate diversity factors, and accounting for environmental conditions, you ensure the generator delivers reliable power without wasteful oversizing. A correctly sized generator provides the right balance of capability, efficiency, and cost.

Frequently Asked Questions

Generator for commercial building?
50-200 kW typical. Include elevator, server room, HVAC, lighting. 0.8 diversity.
De-rating for temperature?
Standard generators rated at 40°C. Each 1°C above de-rates 0.5-1%. At 50°C: lose 5-10%.
Altitude impact on sizing?
At 2000m, NA engine loses 15-20%. Turbocharged less affected. Apply de-rate tables.
100% load continuously?
Standby: 70-80% avg. Prime: 70% avg. Continuous: 100% 24/7.
Fuel consumption calculation?
Diesel: ~0.28 L/kWh at 75% load. 200kW x 0.75 x 0.28 = 42 L/h.
Prime vs standby sizing?
Prime = continuous with variable load. Standby = emergency backup only. Size per application.
Generator growth margin?
Add 10-25% to calculated size. Industrial: 20% minimum. Data center: 25% minimum.
Construction site sizing?
Demand factor 0.5-0.7. Size for largest simultaneous start. 20-500 kVA portable.
Hospital generator size?
500-2500 kVA with N+1 redundancy. NFPA 110 life-safety requirements.
What is diversity factor?
The ratio of actual simultaneous load to total connected load. Typically 0.6-0.9 depending on application.
Undersized generator consequences?
Voltage/frequency dips, overheating, wet-stacking, premature wear, electronics damage.
Data center generator sizing?
IT load + cooling + UPS losses. 0.9 diversity, 25% growth. 500kW IT needs 800-1000 kVA.
What is starting kVA?
The apparent power required to start a motor. Typically 3-7x running kVA. Governs generator sizing.
1-phase vs 3-phase sizing?
1-phase for residential. 3-phase for industrial/motors. Keep imbalance <30%.
Power factor effect on sizing?
Lower PF requires larger kVA. PF correction capacitors can improve.

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