Switchgear is rated in kVA (apparent power) because it must handle the total current flowing in the circuit, which includes both real power (kW) used for work and reactive power (kVAR) used to create magnetic fields in motors and transformers:

• kW represents the actual work performed (useful power)
• kVAR represents reactive power that doesn't perform work but is necessary for equipment operation
• kVA is the vector sum of kW and kVAR (kVA² = kW² + kVAR²)
• Current is directly proportional to kVA, not kW, so switchgear must be sized for the total current

Rating switchgear in kVA ensures it can safely handle the full current load, regardless of power factor.

To determine the appropriate power factor for switchgear sizing:

• Existing Systems: Measure actual PF using a power quality analyzer or check utility bills
• New Installations: Calculate weighted average PF based on load types (see reference chart)
• Conservative Design: Use 0.80 PF for most industrial applications to ensure adequate capacity
• Motor-Dominant Loads: Use 0.70-0.75 PF (motors have lower PF, especially at startup)
• Modern Electronics: Use 0.90-0.95 PF (LEDs, VFDs, and electronics often have built-in PF correction)

When in doubt, consult with a qualified electrical engineer to perform a detailed load analysis for your specific application.

Undersizing switchgear by using kW instead of kVA (ignoring power factor) can have serious consequences:

• Overheating: Higher than rated current causes excessive heat buildup
• Equipment Failure: Premature wear of circuit breakers, contacts, and insulation
• Safety Hazards: Increased risk of arc flash, fires, and electrical accidents
• Nuisance Tripping: Circuit breakers tripping unexpectedly due to thermal overload
• Voltage Drop: Excessive current can cause unacceptable voltage drop in the system
• Code Violations: Non-compliance with NEC, ANSI, and local electrical codes

For example, using 100kW to size switchgear for a 0.7 PF load would result in 143kVA actual demand — a 43% undersizing that could lead to catastrophic failure.

The appropriate oversizing margin for switchgear depends on your specific situation:

• Short-Term (5 years): 20-30% above calculated kVA requirement
• Long-Term (10+ years): 30-50% above calculated kVA requirement
• Rapidly Growing Facilities: 50-75% margin or next standard size
• Stable Loads: 10-20% margin may be sufficient
• Critical Applications: Next standard size regardless of calculation

When selecting switchgear, consider standard ratings (100kVA, 160kVA, 200kVA, 250kVA, 400kVA, 630kVA, 800kVA, 1000kVA, etc.). It's often more cost-effective to select the next standard size rather than a custom rating, even if it provides more margin than calculated.