You can find in brochures, technical papers or even on display of monitoring equipment all the possible combinations: KVAR, kVAr, or kvar for example. But which symbol is the correct one?
What is kvar?
“kvar” (Kilovolt-Ampere Reactive) measures reactive power in AC electrical systems. Unlike active power (KW), which performs actual work, reactive power maintains voltage levels and supports inductive loads (motors, transformers). High kvar increases line losses and reduces efficiency. Power factor correction (using capacitors) minimizes kvar demand, lowering energy costs and improving system capacity. Utilities often penalize low power factor, making kvar management crucial for industrial and commercial operations.
KVAR, kVAr or kvar – which symbol should be used to comply with existing standards?
Generally, people remember that the symbol for volts is “V“, with regards to Mr. Volta, and the symbol for amperes is “A“, with regards to Mr. Ampere.
It is then logical to have the apparent power S, which is the product of voltage by current, symbolized by “VA” (voltampere).
For active power P, it was decided by the Electro-technical Community to use the same unit, (watt) and symbol as the mechanical power, i.e.: “W“, with regards to Mr. Watt.
For reactive power Q, it was decided to introduce the letter “r”. Even if the unit of reactive power is consistent with VA, the International Electrotechnical Commission (IEC) proposed the symbol “var” (with small letters).
On the other hand, the symbol for kilo (103) is k, and the symbol for mega (106) is M.
Then, the multiple of “var” are kvar (kilovar) and Mvar (megavar).
There is also often some confusion concerning the symbol of electrical energy.
The unit of energy is the quantity of energy obtained by dissipating a power of one watt during a period of one second. This unit is called one joule, the symbol is “J“, with regards to Mr Joule.
In electrical engineering, a very practical unit has been introduced, representing the dissipation of a power of one watt during a period of one hour. The unit is then Wh (watt hour), product of power by time.
The multiples are kWh (kilowatt hour) and MWh (megawatt hour).
For reactive energy, the corresponding symbols are varh (var hour), kvarh or Mvarh.
How can kvar be calculated?
To calculate kvar (reactive power), use kvar = kVA × sin(θ) or kvar = √(kVA² – kW²), where:
- kVA = Apparent power
- kW = Real power
- θ = Phase angle between voltage & current
For power factor correction, required capacitor kvar = kW × (tanθ₁ – tanθ₂), where θ₁/θ₂ are initial/final power factor angles.
Understanding letter symbols with IEC 60027-1
More details on letter symbols, such as the use of kvar over kVAr, can be found in IEC 60027-1 (“Letter symbols to be used in electrical technology”). The same symbols are also used in IEEE documents, such as IEEE 519 (“Recommended practices and requirements for harmonic control in Electrical Power Systems”).
*This article was originally published on April 2, 2013 and has been updated for comprehensiveness.
Conversation
Thank you for clarifying the use of var instead of VAr. It may be esoteric but very important to someone who makes a living from selling reactive power products. Do you have a citation of where the IEC officially made the decision to use “var” as you mention in this article? It will be very useful to be able to show doubters the exact reference.
On IEC 60027-7(Edition 1.0 2010-05) the Symbol is “VA” and at “Remarks” section says: “In practice mostly var, kvar, Mvar is used.”