How to Use the Power Factor Capacitor Calculator
Running at a low power factor means more current is needed to deliver the same real power (kW), which increases distribution losses and often triggers a power factor penalty on the electric bill. This calculator takes your load and current/target power factor and computes the leading capacitor bank size (kVAR) needed to reach that target.
The math is based on the difference in reactive power: Q_needed = P x (tanθ1 - tanθ2), where θ1 and θ2 are the phase angles corresponding to the current and target power factors. A lower power factor means more reactive power is being drawn, and the capacitor bank supplies leading reactive power to make up that difference.
Many U.S. utilities apply a power factor penalty or demand adjustment once power factor drops below roughly 0.90-0.95, so targeting around 0.95 is a common choice. Over-correcting past unity power factor (100%) flips the load to leading power factor, which can cause voltage rise and other issues on the utility side — so avoid oversizing the bank.
In practice, loads vary throughout the day, so many facilities pair fixed capacitor banks with an automatic power factor regulator (APFR) that switches capacitor stages in and out as load changes. Final bank sizing, switching scheme, and protection should be reviewed by a licensed electrical engineer against your utility's specific tariff and site conditions.
Frequently Asked Questions
A low power factor means more current is needed to deliver the same real power, which increases distribution losses and often triggers a power factor penalty on the utility bill. Adding capacitors supplies reactive power locally and raises the power factor.
Many utilities apply a penalty below 0.90-0.95 power factor, so targeting 0.95 is common. Over-correcting past unity (100%) can cause leading power factor and voltage rise issues, so avoid over-sizing the capacitor bank.