Diesel Generator Size Calculator
Calculate the appropriate diesel generator size for your industrial or commercial application. Enter your power requirements below.
Continuous Loads
Peak Loads
Site Conditions
How to Size a Diesel Generator?
Understanding Load Requirements
Properly sizing a diesel generator requires careful consideration of various load types and operating conditions:
- Load Classification:
- Continuous Loads: Equipment running constantly (e.g., lighting, servers)
- Intermittent Loads: Equipment running periodically (e.g., pumps, compressors)
- Cyclical Loads: Equipment with regular on/off cycles
- Peak Loads: Maximum power draw during start-up or peak operation
- Power Factor Consideration:
- Most industrial equipment operates at 0.8 power factor
- Lower power factors require larger generator capacity
- Improved power factor reduces required generator size
Common Industrial Applications
| Industry Type | Typical Loads | Recommended Size Range |
|---|---|---|
| Data Centers | Servers, Cooling Systems, UPS | 100-2000 kVA |
| Manufacturing | Production Equipment, Motors | 75-500 kVA |
| Healthcare | Medical Equipment, HVAC | 150-1000 kVA |
| Commercial Buildings | Lighting, Elevators, HVAC | 50-750 kVA |
Common Equipment Power Requirements
| Equipment Type | Running Power (kW) | Starting Power (kW) |
|---|---|---|
| Industrial Motor (50 HP) | 37.3 | 111.9 |
| Air Compressor (25 HP) | 18.7 | 56.1 |
| Industrial Chiller (20 ton) | 22.0 | 66.0 |
| Elevator (15 HP) | 11.2 | 33.6 |
Important Sizing Considerations
1. Environmental Factors
Generator performance is affected by site conditions:
- Altitude: Power output decreases by approximately 1% per 100m above 1000m
- Temperature: Output decreases by about 1% per degree above 40°C
- Installation location: Indoor installations require additional ventilation consideration
- Ambient conditions: Dust, humidity, and salt air affect maintenance requirements
2. Operational Requirements
Consider these operational factors when sizing:
- Duty cycle: Continuous vs. standby operation
- Load profile: Distribution of load over time
- Future expansion: Allow 10-25% capacity for growth
- Maintenance intervals: Larger units may require more frequent service
3. Regulatory Compliance
Ensure compliance with:
- Local emission regulations
- Noise restrictions
- Fuel storage requirements
- Building codes and permits
Frequently Asked Questions
How do I account for motor starting requirements?
Motor starting typically requires 3-6 times the running power. For multiple motors, consider sequential starting or soft starters to reduce peak demand. Our calculator includes this in the peak load calculation section.
What's the difference between prime and standby power ratings?
Prime power is for continuous operation with variable loads, typically rated at 70-80% of standby power. Standby power is for emergency backup only, with a typical annual usage limit of 200 hours. Choose prime power rating for regular use applications.
How much oversizing is recommended?
Generally, add 10-25% capacity above calculated requirements. This provides headroom for future expansion, accounts for load growth, and ensures optimal performance. Critical applications may warrant higher margins.
What role does power factor play in sizing?
Power factor affects the apparent power (kVA) requirement. A power factor of 0.8 means you need a generator rated 25% larger than the actual power (kW) requirement. Improving power factor through correction equipment can reduce generator size needs.
How do I plan for future expansion?
Add 25% to current requirements for future growth. Consider modular solutions or parallel capability if significant expansion is likely. Document current loads thoroughly to facilitate future sizing decisions.
Should I consider redundancy in my generator sizing?
For critical applications, N+1 or 2N redundancy may be necessary. This means having one or more backup generators beyond what's needed for the load. Consider reliability requirements and cost implications when planning redundancy.