kVARh

kVArh, or kilovolt-ampere reactive hour, is a unit used to quantify reactive energy in alternating current electrical systems. It represents the integral of reactive power Q, measured in volt-ampere reactive (VAR), over a period of time. Reactive power is the imaginary component of complex power S = P + jQ and reflects the exchange of energy between inductive and capacitive elements in the network, rather than real energy delivered to a load.

One kVArh equals 1,000 VAR-hours. Over a time interval, if reactive power is roughly constant, the reactive energy is approximately ΔE_Q ≈ Q Δt. For example, a steady 5 kVAR for 2 hours corresponds to about 10 kVArh of reactive energy. In practice, kvarh is used as a measure of the amount of reactive energy that has circulated in the system during an interval, not as a direct measure of dissipated energy.

Usage and context: kvarh is encountered in some electricity markets and in facility power-factor management. It can be used for billing, penalties, or compensation related to poor power factor, and it helps in planning and sizing of capacitor banks and other reactive-power resources. It is important to note that kvarh is not the same as real energy (kWh), since reactive power does not perform net work over a complete cycle. The actual impact on cost and equipment depends on both voltage level and the waveform of the current and voltage.