Power Factor Correction Calculator
Low power factor means your utility has to supply more current than your facility actually uses productively — and many utilities penalize that inefficiency through demand charges billed on apparent power (kVA) or explicit power factor surcharges. This calculator takes your real power load, your current and target power factors, and your demand charge rate, then reports the capacitor bank size needed to correct the power factor, the resulting kVA reduction, and the annual demand charge savings that drop straight to your utility bill. For the broader peak-demand strategy that power factor correction supports, see our Demand Charge Optimizer, and for two related efficiency measures that pair naturally with a power factor correction project, see our Compressed Air System Calculator and Industrial Motor Energy Calculator.
The real (working) power your facility draws — the kW that actually does useful work, distinct from the reactive power inductive loads also draw.
Your present power factor (ratio of real power to apparent power). Typical uncorrected industrial facilities run 0.70–0.85; enter your measured or billed value.
Most utilities require 0.90–0.95 power factor to avoid penalty charges.
Utility demand charges tied to apparent power (kVA) typically range from $5–15/kVA depending on region and rate schedule.
current reactive power (kVAR) − target reactive power (kVAR)
real power (kW) ÷ current power factor
real power (kW) ÷ target power factor
current apparent power (kVA) − target apparent power (kVA)
kVA reduction × demand charge rate ($/kVA) × 12
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →Correcting power factor from 0.75 to 0.95 on a 500 kW load requires about 277 kVAR of capacitor correction -- but the payoff shows up directly on the utility bill: apparent power demand drops from 667 kVA to 526 kVA, a reduction of over 140 kVA. At a typical $8/kVA demand charge, that's over $13,400 a year in avoided demand costs, often paying back capacitor bank installation costs within 1-3 years.
How power factor correction is calculated
This calculator ties the capacitor bank size needed to correct power factor and the resulting demand-charge savings to four inputs: the real power load, the current and target power factors, and the demand charge rate billed on apparent power. Five quantities tie the calculation together.
Current Reactive Power (kVAR) = Real Power (kW) × tan(arccos(Current Power Factor)). Power factor is the ratio of real power to apparent power, and the reactive power a load draws equals the real power times the tangent of the phase angle between them — that phase angle is arccos(power factor). At 500 kW and a 0.75 power factor, that is 500 × tan(arccos(0.75)) = 500 × 0.8819 = 440.96 kVAR of reactive power the utility must supply. Target Reactive Power (kVAR) = Real Power (kW) × tan(arccos(Target Power Factor)); at a 0.95 target power factor, that is 500 × tan(arccos(0.95)) = 500 × 0.3287 = 164.34 kVAR.
Required Capacitor Bank Size (kVAR) = Current Reactive Power (kVAR) − Target Reactive Power (kVAR). A capacitor bank supplies reactive power locally so the utility no longer has to deliver it; the size needed is simply the gap between your current and target reactive power demand. At 440.96 kVAR current and 164.34 kVAR target, that is 440.96 − 164.34 = 276.62 kVAR of correction.
Current Apparent Power (kVA) = Real Power (kW) ÷ Current Power Factor; at 500 kW and 0.75, that is 500 ÷ 0.75 = 666.67 kVA. Target Apparent Power (kVA) = Real Power (kW) ÷ Target Power Factor; at 500 kW and 0.95, that is 500 ÷ 0.95 = 526.32 kVA. kVA Reduction = Current Apparent Power (kVA) − Target Apparent Power (kVA); at 666.67 kVA and 526.32 kVA, that is 666.67 − 526.32 = 140.35 kVA of apparent power the utility no longer has to deliver.
Annual Demand Charge Savings ($/year) = kVA Reduction × Demand Charge Rate ($/kVA) × 12. Utilities that bill demand on apparent power (kVA) inherently penalize low power factor, because a low power factor inflates the kVA the utility must reserve for the same real work; correcting power factor shrinks that kVA and the monthly demand charge with it. At a 140.35 kVA reduction, $8/kVA, and 12 months, that is 140.35 × 8 × 12 = $13,473.68 per year. Two notes on the model. First, it assumes a simple fixed capacitor bank and a linear, steady-state load — real facilities have varying load profiles and harmonic content that can affect capacitor sizing and may require detuned or switched banks. Second, it captures only the demand-charge savings from kVA reduction; facilities billed under explicit power factor penalty clauses (rather than kVA-based demand) may see additional savings not modeled here. Data sources: IEEE 1415 standard for power factor correction; utility demand charge structures from FERC and regional transmission organization tariffs; capacitor bank sizing methodology from IEEE and NEMA standards; reactive power calculations from AC circuit theory and power systems engineering; industrial power factor data from facility energy audits and utility billing analysis.