Convert apparent power (kVA) to reactive power (kVAR) for power factor correction and electrical system analysis. Calculate reactive power requirements accurately.
Power Quality | Version 2.1
Choose calculation method based on available data
Enter the total apparent power in kilovolt-amperes
Power factor range: 0.1 to 1.0 (0.8 is typical for industrial loads)
Inductive loads (motors) create lagging power factor
Reactive Power: 0 kVAR
Real Power: 0 kW
Apparent Power: 0 kVA
Power Factor: 0
Phase Angle: 0°
Enter values above to see detailed calculations
Method 1: Using Power Factor
kVAR = kVA × sin(φ)
where sin(φ) = √(1 - PF²)
Method 2: Using Real Power
kVAR = √(kVA² - kW²)
Power Triangle Relationship
kVA² = kW² + kVAR²
Problem: Calculate kVAR for a system with 100 kVA apparent power and 0.8 power factor (lagging)
φ = arccos(PF) = arccos(0.8) = 36.87°
sin(φ) = sin(36.87°) = 0.6
Alternatively: sin(φ) = √(1 - PF²) = √(1 - 0.8²) = √(1 - 0.64) = √0.36 = 0.6
kVAR = kVA × sin(φ)
kVAR = 100 × 0.6 = 60 kVAR
kW = kVA × cos(φ) = 100 × 0.8 = 80 kW
Reactive power (kVAR) is the power used to create and maintain magnetic fields in inductive equipment like motors, transformers, and inductors. Unlike real power (kW) which performs useful work, reactive power oscillates between the source and load without being consumed. It's crucial because: it's required for motor operation and transformer magnetization, poor reactive power management leads to higher utility bills, excessive reactive power causes voltage drops and system inefficiency, and utilities often charge penalties for poor power factor. Understanding kVAR helps optimize electrical systems and reduce energy costs.
The choice depends on your load type: Lagging reactive power (positive kVAR) occurs with inductive loads like motors, transformers, and inductors where current lags behind voltage. This is the most common scenario in industrial facilities. Leading reactive power (negative kVAR) occurs with capacitive loads like capacitor banks, over-excited synchronous motors, and long transmission lines where current leads voltage. Most industrial facilities have lagging power factor due to motor loads and require capacitive compensation. Use lagging for typical industrial calculations and leading when analyzing capacitor banks or power factor correction systems.
Choose the method based on available data: Use the Power Factor method when you know the system power factor from power quality measurements, utility bills, or equipment specifications. This is common for overall system analysis and power factor correction planning. Use the Real Power (kW) method when you have actual power consumption measurements from energy meters, load studies, or individual equipment ratings. This method is preferred for detailed load analysis and when combining multiple loads with different power factors. Both methods give identical results when applied correctly.
Reactive power significantly impacts electricity costs through several mechanisms: Many utilities charge demand charges based on kVA rather than kW, so high reactive power increases bills even without additional real power consumption. Poor power factor penalties are common for commercial and industrial customers with power factors below 0.85-0.9. Reactive power causes higher currents for the same useful power, leading to increased transmission losses and infrastructure costs. Some utilities offer power factor bonuses for maintaining high power factors above 0.95. A facility with 100 kW load at 0.7 power factor draws 143 kVA, while the same load at 0.95 power factor draws only 105 kVA, significantly reducing demand charges.
kVA to kVAR calculations are essential in numerous electrical applications: Power factor correction system design to determine required capacitor bank size, electrical system analysis for load flow studies and voltage regulation, motor starting studies to calculate reactive power requirements during startup, transformer sizing to account for reactive power in addition to real power, utility billing analysis to understand demand charges and power factor penalties, and renewable energy integration to manage reactive power in grid-connected systems. Industrial facilities use these calculations for energy audits, electrical system optimization, and compliance with utility power factor requirements.