Introduction #

Diversity factor is one of the most misunderstood concepts in factory load calculation. Apply it incorrectly, and you'll either waste money on oversized equipment or face constant breaker trips from undersized systems. This guide explains what diversity factor actually means, how to determine realistic values for your facility, and how to apply it correctly in calculations.

What is Diversity Factor? #

Diversity factor accounts for the fact that not all equipment operates simultaneously or at full capacity. It's the ratio of actual maximum demand to the sum of individual maximum demands.

Mathematical Definition #

Diversity Factor = Sum of Individual Max Demands ÷ Actual Maximum Demand

Or inversely:
Demand Load = Connected Load ÷ Diversity Factor

Key Point: Diversity factor is always ≥ 1.0. Higher values mean more diversity (less simultaneous operation).

Why Diversity Factor Matters #

In a typical factory:

  • Not all machines run at the same time
  • Machines don't always operate at full load
  • Production schedules create natural load variations
  • Maintenance and breaks reduce simultaneous operation

Without diversity factor: You'd size for worst-case scenario (everything on, everything at full load)
With diversity factor: You size for realistic maximum demand

Typical Diversity Factors for Industrial Equipment #

Production Equipment #

Equipment Type Diversity Factor Notes
Continuous process machines 0.85-0.95 Run 24/7, high simultaneity
Batch process machines 0.70-0.85 Intermittent operation
Assembly line equipment 0.75-0.90 Coordinated but not all at peak
CNC machines 0.60-0.80 Varies by production schedule
Manual workstations 0.50-0.70 Operator-dependent

Support Systems #

System Type Diversity Factor Notes
Lighting (production) 0.90-0.95 Most lights on during shifts
Lighting (office) 0.85-0.95 Varies by occupancy
HVAC (production) 0.70-0.85 Climate-dependent
HVAC (office) 0.75-0.90 Occupancy and schedule
Compressed air 0.80-0.90 Multiple users, varying demand
Material handling 0.60-0.80 Forklifts, conveyors intermittent

Special Equipment #

Equipment Type Diversity Factor Notes
Welding equipment 0.30-0.50 Very intermittent, high peak
Resistance heating 0.70-0.85 Temperature control cycles
Induction heating 0.60-0.80 Process-dependent
Battery chargers 0.40-0.70 Charging cycles

How to Determine Diversity Factor for Your Facility #

Method 1: Measurement-Based (Most Accurate) #

Step 1: Install power monitoring equipment
Step 2: Measure actual maximum demand over 1-3 months
Step 3: Calculate connected load from nameplates
Step 4: Calculate diversity factor:

Diversity Factor = Connected Load ÷ Measured Maximum Demand

Example:

  • Connected load: 500 kW
  • Measured maximum demand: 350 kW
  • Diversity factor: 500 ÷ 350 = 1.43

Method 2: Industry Standards (Quick Estimate) #

Use typical values for your industry:

Industry Type Typical Overall Diversity Factor
Light manufacturing 0.70-0.80
Heavy manufacturing 0.65-0.75
Warehouses 0.60-0.70
Food processing 0.75-0.85
Chemical processing 0.80-0.90
Data centers 0.85-0.95

Method 3: Load Category Analysis (Recommended) #

Break down by load category and apply appropriate factors:

Example Calculation:

Category Connected (kW) Diversity Factor Demand (kW)
Production machines 300 0.75 225
Welding 100 0.40 40
Lighting 50 0.95 47.5
HVAC 80 0.80 64
Compressed air 40 0.85 34
Office 30 0.65 19.5
Total 600 Weighted: 0.65 430

Overall diversity factor: 600 ÷ 430 = 1.40

Common Mistakes in Applying Diversity Factors #

Mistake 1: Using Unity (1.0) for Everything #

Error: Assuming all equipment operates simultaneously
Impact: 30-40% oversized equipment
Correct: Apply realistic factors based on equipment type

Mistake 2: Overestimating Diversity #

Error: Using 0.50 for all equipment to "be safe"
Impact: Undersized system, breaker trips
Correct: Use measured or industry-standard values

Mistake 3: Ignoring Load Type #

Error: Using same factor for motors and lighting
Impact: Incorrect kVA calculations
Correct: Different factors for different load types

Mistake 4: Not Accounting for Future Changes #

Error: Using current diversity without considering expansion
Impact: System can't handle growth
Correct: Plan for reduced diversity as facility grows

Real-World Example: Applying Diversity Factors #

Facility Overview #

Medium-sized manufacturing plant:

  • 50 production machines (10 kW each)
  • 5 welding stations (25 kW each)
  • Lighting: 30 kW
  • HVAC: 50 kW
  • Compressed air: 40 kW

Step 1: Calculate Connected Load #

Production: 50 × 10 = 500 kW
Welding: 5 × 25 = 125 kW
Lighting: 30 kW
HVAC: 50 kW
Compressed air: 40 kW
Total Connected: 745 kW

Step 2: Apply Diversity Factors #

Category Connected (kW) Diversity Factor Demand (kW)
Production machines 500 0.75 375
Welding 125 0.40 50
Lighting 30 0.95 28.5
HVAC 50 0.80 40
Compressed air 40 0.85 34
Total Demand 745 527.5

Step 3: Calculate Overall Diversity Factor #

Overall Diversity Factor = 745 ÷ 527.5 = 1.41

This means the actual maximum demand is 29% lower than connected load.

Step 4: Equipment Sizing #

Assuming power factor 0.85 and 20% safety margin:

Design Load = 527.5 × 1.20 = 633 kW
Design kVA = 633 ÷ 0.85 = 745 kVA

Selected Transformer: 750 kVA
Selected Breaker: 1000 A (745 kVA ÷ (√3 × 400V) = 1075 A, with margin)

Factors Affecting Diversity Factor #

1. Production Schedule #

  • Single shift: Lower diversity (more equipment on)
  • Multiple shifts: Higher diversity (equipment shared)
  • 24/7 operation: Highest diversity (equipment rotation)

2. Process Type #

  • Continuous process: High diversity factor (0.85-0.95)
  • Batch process: Medium diversity (0.70-0.85)
  • Job shop: Low diversity (0.60-0.75)

3. Facility Size #

  • Small facilities: Lower diversity (fewer options)
  • Large facilities: Higher diversity (more equipment, more variation)

4. Equipment Redundancy #

  • No redundancy: Lower diversity (everything must work)
  • Redundant systems: Higher diversity (backup available)

Engineering Best Practices #

1. Document Your Assumptions #

Always record:

  • Diversity factors used
  • Source of factors (measured, standard, estimated)
  • Date of determination
  • Any special considerations

2. Validate with Measurements #

After installation:

  • Measure actual maximum demand
  • Compare to calculated demand
  • Adjust factors for future projects

3. Review Periodically #

Diversity factors change over time:

  • New equipment added
  • Production patterns change
  • Facility expansion
  • Review every 2-3 years

4. Use Conservative Values for Critical Systems #

For safety-critical or production-critical systems:

  • Use lower diversity factors
  • Add extra safety margin
  • Consider worst-case scenarios

Integration with Factory Load Calculator #

Our Factory Load Calculator uses industry-standard diversity factors automatically. However, understanding diversity factor helps you:

  • Interpret calculator results correctly
  • Adjust for your specific facility
  • Validate calculator recommendations
  • Plan for future changes

Calculate your load: Factory Load Calculator

Conclusion #

Diversity factor is essential for realistic factory load calculations. It accounts for the reality that not all equipment operates simultaneously, preventing costly over-sizing while ensuring adequate capacity. Use measured values when possible, industry standards as starting points, and always document your assumptions. Remember: diversity factor varies by equipment type, production schedule, and facility characteristics—there's no one-size-fits-all value.