What is power factor correction?

Power factor correction (PFC) is the process of adding capacitors to an electrical system to reduce reactive power demand and bring the power factor closer to unity (1.0). This reduces current draw, lowers losses, and avoids utility penalties.

How do I calculate the capacitor size needed?

Qc = P × (tan φ1 − tan φ2), where P is active power in kW, φ1 = arccos(PF_current), φ2 = arccos(PF_target). The result Qc is in kVAR. For capacitance in μF: C = Qc × 10⁹ / (2π × f × V²).

What target power factor should I aim for?

Most utilities require PF ≥ 0.90 to avoid penalties. A target of 0.95–0.98 is recommended. Avoid overcorrecting above 1.0 (leading PF) as this can cause voltage rise and resonance issues.

What are the benefits of power factor correction?

Benefits include: reduced electricity bills (avoiding reactive power charges), lower current in cables (freeing capacity), reduced I²R losses, improved voltage regulation, and compliance with utility requirements.

Should I use fixed or automatic capacitor banks?

Fixed banks are suitable for constant loads (e.g., a single large motor). Automatic banks with contactors and a PF controller are better for varying loads — they switch capacitor steps on/off to maintain target PF.

Free Engineering Tool

Power Factor Correction Calculator

Calculate required capacitor bank kVAR and μF to improve power factor. Qc = P × (tan φ₁ − tan φ₂).

kVAR Sizing Capacitor μF Power Triangle

Active Power P (kW)

Current Power Factor (cos φ₁)

Target Power Factor (cos φ₂)

System Voltage (V, line-to-line)

Frequency (Hz)

Capacitor Connection

Quick presets

Results

Required Capacitor Bank

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Capacitance per Phase

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Current Before (S₁ / I₁)

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Current After (S₂ / I₂)

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Current Reduction

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Reactive Power Compensation

Capacitance in μF

Example — 100 kW load, PF 0.75 → 0.95

tan φ₁ = tan(acos 0.75) = 0.8819, tan φ₂ = tan(acos 0.95) = 0.3287

Qc = 100 × (0.8819 − 0.3287) = 55.3 kVAR

⚠️ Note: Do not overcorrect above unity PF (leading). This can cause voltage rise, resonance with transformers, and equipment damage.