Power factor is the ratio of real power to apparent power in an AC circuit, expressed as a decimal between 0 and 1 or a percentage up to 100 percent. A power factor of 1.0 (or 100 percent) indicates all electrical power is being used productively, while lower factors indicate wasted reactive power. Most HVAC systems operate at power factors between 0.80 and 0.95.
Technical Details
Power factor is calculated as the cosine of the phase angle between voltage and current waveforms. AC motors in compressors and fans typically have power factors between 0.75 and 0.90 due to inductive reactance. Power factor improves with capacitor installations, which are common in HVAC systems. Three-phase commercial systems are more sensitive to power factor variations than single-phase residential systems.
Energy Efficiency Implications
Lower power factors require higher current draw to deliver the same real power output, increasing transmission losses and energy costs. Industrial facilities with power factors below 0.90 may face utility penalties. Adding capacitors to HVAC systems improves power factor and reduces electricity consumption by 5 to 15 percent.
Commercial Relevance
Utilities monitor power factor on large commercial accounts. Improving power factor through equipment upgrades or capacitor installation reduces demand charges and improves overall system efficiency for HVAC operations.