Calculate the kVAR capacitor needed for power factor correction. Enter current and target power factors with kW load to find required capacitance.
Power factor (PF) is a measure of how efficiently electrical power is being used. A power factor of 1.0 (unity) means all power is doing useful work. A low power factor (0.70–0.85) means a significant portion of current is reactive — flowing back and forth without doing work, but still creating losses in the electrical system.
Utilities charge commercial and industrial customers penalties for low power factor (typically below 0.90 or 0.95) because reactive current increases grid losses. The standard correction method is installing capacitor banks that generate reactive power locally, reducing the reactive current drawn from the grid.
This calculator determines the kVAR (kilovolt-ampere-reactive) rating of the capacitor bank needed to improve power factor from a current value to a target value. Use it to size capacitor banks, estimate cost savings from avoiding penalties, and optimize your facility's electrical efficiency.
This measurement provides a critical foundation for energy auditing and sustainability reporting, helping organizations meet regulatory requirements and voluntary environmental commitments.
Power factor penalties can add 10–30% to a commercial electric bill. This calculator sizes the capacitor bank needed to correct power factor and eliminate those penalties, often paying back the investment in 6‒18 months. Having accurate metrics readily available streamlines utility bill analysis, budget forecasting, and investment planning for energy efficiency projects and renewable energy installations.
kVAR = kW × (tan(φ₁) − tan(φ₂)) where φ₁ = arccos(PF₁) and φ₂ = arccos(PF₂)
Result: 96.0 kVAR
tan(arccos(0.78)) = 0.8026, tan(arccos(0.95)) = 0.3287. kVAR = 200 × (0.8026 − 0.3287) = 200 × 0.4739 = 94.8 kVAR. A 100 kVAR capacitor bank would be the standard size selected.
In AC circuits, inductive loads draw current that lags voltage by a phase angle. This lagging component is reactive power (kVAR). It doesn't do useful work but creates losses in conductors and transformers. Capacitors generate leading reactive power that cancels the lagging component, reducing total current.
Fixed capacitor banks provide constant correction, suitable for steady loads. Automatic switched banks use a PF controller to switch capacitor stages on/off as loads change, maintaining optimal PF. Detuned capacitor banks include reactors to prevent harmonic resonance in facilities with variable frequency drives.
Capacitor banks cost $25–75 per kVAR installed. A 100 kVAR bank costs $2,500–$7,500. If the penalty savings are $500–$1,000/month, payback is 3‒15 months. Additional benefits include reduced I²R losses and freed-up transformer capacity.
Power factor is the ratio of real power (kW, doing useful work) to apparent power (kVA, total power drawn). A PF of 0.80 means only 80% of the current is doing useful work. The remaining 20% is reactive current that creates losses.
Low power factor means higher current for the same real power, causing greater losses in transformers, cables, and generators. The utility must maintain larger infrastructure to supply this extra current, and the penalty recovers those costs.
Inductive loads are the primary cause: motors (especially lightly loaded ones), transformers, fluorescent lighting ballasts, and induction furnaces. Variable frequency drives and electronic loads can also reduce power factor.
The size depends on your real power (kW), current PF, and target PF. This calculator provides the exact kVAR needed. Standard capacitor bank sizes come in 25, 50, 100, 200, and 300+ kVAR. Choose the next size up from the calculated value.
Savings depend on your utility's penalty structure. Typical penalties add 2–30% to the electric bill. For a facility with a $5,000/month bill and a 15% PF penalty, correction saves $750/month or $9,000/year.
Yes. Over-correction creates a leading power factor, which can cause voltage rises, resonance issues, and even penalties from some utilities. Always target 0.95–0.98 rather than 1.0, and use automatic switched capacitor banks for variable loads.