Calculate power factor, phase angle, real power (kW), reactive power (kVAR), and apparent power (kVA) for AC systems, with correction analysis.
Enter real and apparent power, or real and reactive power, or phase angle
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Power factor is a critical metric in AC electrical systems that measures how efficiently electrical power is being used. Our calculator helps you analyze the power triangle, determine real, reactive, and apparent power, and calculate capacitor requirements for power factor correction — for both single-phase and three-phase systems, including wye/delta capacitor sizing.
Power factor (PF) is the ratio of real power (P) to apparent power (S), representing how efficiently electrical power is converted to useful work. A power factor of 1.0 (unity) is ideal, meaning all power is used productively. Low power factor indicates wasted energy due to reactive power from inductive or capacitive loads. In single-phase systems apparent power is S = V × I; in three-phase systems it is S = √3 × V_LL × I, where V_LL is the line-to-line voltage. Power factor is defined by the power triangle, where real (P), reactive (Q), and apparent (S) power relate as S² = P² + Q² — the standard IEEE framework for AC power; correcting a low PF with capacitors cuts wasted reactive power.
Power Factor Formulas
Calculate power factor correction for induction motor loads.
Determine if power factor penalties apply and calculate savings from correction.
Calculate required capacitance for power factor improvement.
Size transformers, cables, and switchgear based on apparent power requirements.
Utilities charge penalties for low power factor, often below 0.90 or 0.95.
Higher power factor reduces current flow, freeing up transformer and cable capacity.
Lower current means reduced I²R losses in conductors and equipment.
Correcting power factor reduces voltage drop along feeders, stabilizing voltage at the load.
Low power factor is typically caused by inductive loads like motors, transformers, and fluorescent lighting ballasts. These loads draw reactive power that oscillates between the source and load without doing useful work.
Lagging power factor occurs with inductive loads where current lags voltage (most common in industrial settings). Leading power factor occurs with capacitive loads where current leads voltage. Motors and transformers cause lagging PF.
Capacitors provide leading reactive power that cancels the lagging reactive power from inductive loads. This reduces the total reactive power and improves the power factor toward unity.
Most utilities require power factor above 0.90 or 0.95 to avoid penalties. Some industrial facilities aim for 0.95+ to maximize savings and equipment efficiency.