Generator Selection Criteria: Designing for Maximum Demand, Future Loads & Efficiency

elearning@ensemble
Sep 2
2 min read

Choosing the right generator is not simply about kVA rating—it involves a thorough understanding of maximum demand, load patterns, efficiency, and future scalability. A poorly selected generator can lead to overloading, fuel wastage, higher emissions, and frequent breakdowns.

This blog will guide you through the essential criteria for generator selection, ensuring long-term reliability, cost-effectiveness, and compliance with Indian and international standards.

1. Assessing Maximum Demand (MD)

1.1 What is Maximum Demand?

Maximum Demand is the highest electrical load a facility draws over a specified period. It forms the basis for selecting a generator of the right size and capacity.

1.2 How to Calculate Maximum Demand

Use load surveys and historical consumption data.
Apply demand factors for different load types (lighting, HVAC, industrial machinery).
Example: A building with a connected load of 600 kW, operating at a demand factor of 0.8, will have a MD = 480 kW.

2. Considering Future Load Expansion

Selecting a generator only for present requirements can be risky. Always consider:

Planned building expansions (extra floors, new equipment).
Load diversity (seasonal loads like HVAC).
A general 25–30% margin is recommended for scalability.

✔ For example: If MD is 500 kW, a 625 kVA generator may be a suitable choice to account for future loads.

3. Efficiency & Loading Factor

3.1 Loading Factor

Generators operate best at 70–80% load.

Underloading leads to wet stacking and reduced fuel efficiency.
Overloading causes overheating and mechanical stress.

3.2 Fuel Efficiency

Choose generators that meet CPCB IV+ emission norms.
Ensure specific fuel consumption (SFC) is optimized at your operating load.

4. Power Factor & Load Type

Most generators are rated at 0.8 power factor lagging.
For industries with high inductive loads (motors, compressors), kVA rating must be adjusted.
For non-linear loads (IT data centers), ensure compatibility with harmonic filters.

5. Standards & Compliance

✔ CPCB IV+ Norms (India) – for emission and noise control.✔ IS/IEC Standards – ensure compliance with safety and performance requirements.✔ ECBC Guidelines – for energy-efficient building systems.

6. Best Practices for Generator Selection

✅ Conduct a detailed load study before procurement.✅ Add future load margins (typically 25–30%).✅ Choose generators with digital controllers for monitoring.✅ Ensure AMC support and spare parts availability.✅ Verify fuel type availability (diesel, gas, hybrid) in your region.

Wrapping Up

Generator selection requires careful consideration of maximum demand, future load growth, efficiency, and compliance standards. A properly sized generator ensures cost savings, reliability, and regulatory adherence, making it a crucial investment for industries, commercial spaces, and residential complexes.

In the next blog, we will cover Testing of Generators: Type Tests, Routine Tests & On-Site Testing.