Reactive power is the portion of electrical power that oscillates between components without producing useful work, measured in volt-amperes reactive (VAR). Unlike real power which performs actual cooling or heating, reactive power results from inductive and capacitive elements in AC circuits. HVAC motors generate reactive power due to their inductive nature.
Technical Details
Reactive power is measured in VAR or KVAR (kilovolt-amperes reactive). It lags or leads voltage depending on whether the circuit contains inductive or capacitive elements. HVAC compressor motors generate reactive power because of motor windings’ inductance. The relationship between real power, reactive power, and apparent power forms the power triangle: Apparent Power = √(Real Power² + Reactive Power²). Systems with high reactive power require larger conductors and transformers.
HVAC System Effects
Compressors and fan motors contribute 20 to 30 percent reactive power to total apparent power consumption. Utilities reduce reactive power by installing capacitors, typically 5 to 20 KVAR units on commercial HVAC systems. Excessive reactive power increases utility demand charges.
Efficiency and Cost Management
Reducing reactive power improves power factor and decreases electricity costs. Power factor correction capacitors are standard installations on commercial HVAC systems to minimize reactive power impact.